I've used AliExpress & Ebay predominantly. No problems with Ali other than shipping time which is a common issue regardless if originating from Asia. I have not used Bangood but for no particular reason. Sometimes I see the exact same item and/or even same seller across all 3 platforms.
Maybe its me or the particular machining type stuff I'm looking at, but seems like Ali has increasingly more items identified for shipping by DHL or similar faster courier mode vs. the classic TheSlowBoat free shipping or minimal shipping cost mode. That expedited / trackable? mode cost can add substantially. Maybe its a trend or maybe just select sellers but I have noticed expedited is the ONLY way they ship, no SlowBoat is even available. Maybe they are bigger more industrial sellers or maybe they have had too many delivery issues? The expedited seems a bit cheaper than ordering the same item out of USA weight/size factored by USPS, but this is just a generalization.
Another interesting thing is going to be how tariffs will/will not apply to us 2019+. If a USA company imports a tariff add Chinese item, I suspect that will be a cost add to them & this dinger will get passed onto a CDN order. That's before any new-Nafta, GST etc. Now if you bought the exact same item from China direct, we don't have these trade war tariffs (yet) so maybe mitigating these dispute tariffs? Its a mess, that's all I know.