My personal preference is either Banggood or Gearbest. I've ordered Xiaomi stuff from eBay and it took forever and had no tracking of any kind. Kind of a pay and pray experience. Same experience with most AliExpress sellers. Plus I prefer the protection of PayPal purchases rather than handing my credit card info over to whomever at AliExpress.
Gearbest has the best deals on the Aqara hub right now. Honestly, the prices between the two fluctuate so much, I just check both and choose. You can also get a Mijia Multi-mode gateway for less. If you're just interested in getting sensors into HE via HomeKit, then you might try that one. I have the Aqara HomeKit Gateway, but just ordered a Mijia Multi-Mode HomeKit compatible gateway to try. It doesn't have the siren/doorbell/nightlight features of the Aqara Gateway, and it cannot use the Aqara app (has to be the Mi Home app), but it is Zigbee 3.0 and does have the bluetooth mesh capability, so that will be interesting for the future. It supports all the Mijia devices and all the Aqara sensors.
Only thing I'm not sure about on the Mijia Multi-mode gateway is, how many end devices can it support. Official docs and many listings say 32. But HomeKit news indicated that an update moved it up to 64. Not sure if that's correct for sure though.
