Apples to oranges comparison when comparing with AliExpress.
AliExpress is more like eBay - a marketplace, where anyone can come and sell their gadget or gizmo.
Banggood operates more like a consumer goods chain - they pick whatever they think will sell from the Chinese marketplace and then offer it on their store. They also pre-position the larger/heavier/more expensive items that are likely to be popular to their local warehouses around the world.
By consequence Banggood is unlikely to carry a lot of things that appeal only to niche markets.
However, if you need something that they actually stock in a local warehouse (e.g. 3D printers, some tools, etc.), then you can get a really good deal and have it at your doorstep within a few days, unlike with AliExpress. Ali has also warehouses now but most of the interesting items are not locally stocked and have to ship from China.
My problem with the search on these places is mainly that it, frankly, sucks. It is trivially gamed by various keyword salads, it is almost impossible to filter the results and even when you somewhat get what you want the ordering is not based on your criteria but which vendor paid for ads (AliExpress) or what the store wants to push (Banggood).
And they’re even worse in non-Chinese languages other than English, and even that requires understanding the curious AliExpress dialect of English, where long-lead LEDs are “long hair LED” and dice for games are “resin deciders”.)
That's because all of it is machine translated from Chinese/English. They translate even reviews, so you get complete gibberish. I do wish there was a way to permanently disable that BS, switching the language back to English is the first thing I am doing every time I use the website.