This is my personal experience with buying from site like SheInside & AliExpress. Nothing was given to me for free from either site, and both had positive and negative buying experience. Base on my review, I'm sure if you wanted to; you can buy from site like Oasap and LightInTheBox, which I believe are very similar in concept to the sites mention above.

Site/Navigation

SheInside is very easy to navigate because of how its site is lay out. It is also cleaner, and more targeted toward fashion purchases then anything else. The only issues I have with them are their searches, and how it is not as accurate compared to AliExpress. For example, if you are searching for a yellow shirt, the search result will show all different color shirts, and not just the yellow shirt you looking for (even when you click on the actually product to see a yellow version of that shirt).

AliExpress on the other hands sells everything, and I mean everything. I would say AliExpress would be comparable to eBay & Amazon but from China. Because AliExpress is such a huge market place, it is not easy to navigate, unless you know what you are doing, and you know what you are looking for.  They have a  pretty good search engine for the most part, and that made them really hard to beat.

If I have to rate it, and I was basing it  purely on ease of use for a newbies, then the winner for site/navigation experience will have to go to SheInside, and that is only due for ease of shopping.

Pricing

SheInside & AliExpress pricing used to be comparable, and was cheaper than American stores, but now the prices has gone up for a lot of their items. So unless you are buying something that is hard to find or extremely rare, I don't believe their site are worth the hassle when you can find something similar or in season at your current country.

Winner for affordable pricing would be AliExpress; because of its flea market type pricing (you will see multiply sellers selling the same items at different prices). Note: If you go super cheap, then the item you buy will reflect that pricing, and you are not offered a guarantee (for the most part) that the product you getting will match the pictures as advertised. So from my experience, the higher the price, the better quality you get.

Please note the example I show you above (second image) is an example pure and simple, note that the seller has no feedback, and he/she is selling this skirt for way too much. I'm just showing you the concept of the flea market pricing at AliExpress.

Quality of Products

The people that tend to buy from these sites are looking for either cheap goods or rare items. I fall under the rare items (or hard to find items).Even though you know the items are super cheap, you still hope that you can at least get a couple of wears from them. I find if you spend less, the quality of what you get there will also look and feel cheap.

If you pay more, you are gambling with your money, because A) you don't know if the product is worth the price you paying for, and B) you also don't know how it will fit, because compared to the USA and European size standard, Asian are considered petite and their size run SMALL. Below is my experience with both sites.

I find if I go to quality store on AliExpress, the clothes are really nice, and the quality is up to par, but you have to be a VERY experience shopper to buy from AliExpress. You have to look at so many factors before even hitting the buy button. I something like to visit store that have a higher price margin items, with better review to at least assure myself that I'm getting something good. I sometime spent a couple of minutes combing through reviews (using Google translate to translate some at times) and then looking at the actually picture of the product before I even buy an item from there.

Below is an example of what I look for when I'm viewing pictures of the product from either site, I like to see the product image of stitching and the fabric.

SheInside for the most part can sell pretty good items, but it is truly a hit and misses there sometime. I had an experience of pre-ordering an item base on the picture (which was an American modal), and the quality appeared to be good at the time I purchase that item. When I got the item, the quality was way different, and when I went back to the item to leave review, the picture was change to an Asian modal with a lower quality version of the product I purchase. This I what I considered a bait and switch, and that is why I stop buying from SheInside.

That is why I like to state that sometime it is not worth the hassle to buy from site likes these, unless the item is hard to find or rare.

Winner of Quality of Products goes to AliExpress, and only if you are a good and well train shopper. Which you will be after fully reading this review ^_-.

Delivery

Both site can be considered slow compare to American & European delivery time, since it can take anywhere between 2-6 week for delivery of your items. SheInside is terrible though with the processing time, as well as the delivery time. Another negative against SheInside is that they charge for shipping, if your cart is less than $30. AliExpress sellers don’t charge a shipping rate most of the time.

So the winner for delivery goes to AliExpress hands down. AliExpress has free shipping, and a much faster shipping and processing time depending on the sellers you buy from.

Scam Factor

Both sites are not a scam, their customer service suck, but their sites are not fake. The people that use the site to sell their goods are the ones you have to worry about (as an example to eBay).

I notice a lot of the sellers use other "known" website images to depict their items to sell, and those are the one that tend to be shady if their pricing are super cheap. Most items on both sites tend to be knock-off of some fashion item or another. I personally like some fashion items that come from Korea, and China, and that why I purchases some stuff from there. I normally try not getting stuff that are knock-off of American fashion.

SheInside had some hit, and misses as far as representing their actually product, and so has AliExpress. I'm only giving this to AliExpress by a little bit, because some of their sellers do actually show images of what they are actually selling.  As an example shown on your right, this is an item I purchase from one seller that was clearly legit.

Honest Reviews

AliExpress truly is the best place to see honest review! At AliExpress, you can only review an item or seller if you actually purchased from them.

SheInside lets anyone review their items or clothes, you just have be a register user, and that just defeat the whole purpose to me (plus they offer reviewers 10 SheInside Points on top of that).

Winner here for "honest review" hands down goes to AliExpress.

Example of AliExpress Review System

Conclusion: Personally I like buying from AliExpress, because I always had a much better experience with them, and know what to look for vs. when I first started. I also really like the fact that their reviews are from HONEST BUYERS, unlike SheInside that lets anyone review their stuff.

If you new to buying from site like these, and you don't want to read this long post, I suggest getting your feet wet with SheInside. To tell you the truth, if you don’t want to read this post, in my honest opinion, I would suggest you to save your money, and don’t buy from either of these site.

If you can take your time, then read the step below and buy from AliExpress.

How to Buy

1) Know your "body" measurements!!!!! That is the most important factor when buying from these sites.

You need to understand that the clothes are coming from China, and they are SMALL compared to the American/European Standards. So please, and I mean PLEASE, look at their measurement, and description of each of the clothes you are "considering" buying. Most good seller’s on AliExpress (and SheInside) states the dimension of each item.

So if you want to buy from either site, get a measuring tape, and start measuring your bust, waist, sleeves, etc.

Check out below, I show you an example of what not to look at. Their sizing are often incorrect. I like to look at their measurement. As you can see below, the largest size they carry is an American Large. 

Tip: If you wear a medium in US size, mostly likely you be wearing Large and Extra Large (something XXL). Also make sure you check the sleeve length of each long sleeve items you thinking of buying. I'm tall with board shoulders, and long arms, and I only purchase long sleeve items that clearly states 62 or more cm for the sleeve.

2) Check their images for quality of their clothes, and the type of material use. Usually that will be a dead giveaway whether the items are good or not. Try not fall for the images that are taken by other site. They tend to be knock offs.

3) Check seller review, as well as review of the item you are purchasing. SheInside is terrible in regards of that.

4) Be willing to gamble just a little, and pay a little higher for an item you really want (usually the material and stitching are better). Also try to stay away from items where you know the fit will not be the same, especially if you are a westerner, and you are tall. Example, I have not purchase any pants from there or any long rompers. I just have a feeling that their version will be consider very "high waters" on me lol.

5) Only shop there if the items you want can't be found anywhere else.

Hope this post help make buying from these site a little bit easier. Sorry for the long post, but this will help you in the long run. I wish I found something like this when I first started buying from either site.