Xiaomi Gateway and Sensors Version Confusion

For the Xiaomi Smarthome gang who have these, what's the difference between the Xiaomi Gateway Version 1 and the Upgraded version?

Is the upgrade one worth the extra $$. Will mainly be pairing it up with the sensors for home security.

I think there's also 2 version of the Sensors too? One Aqara and one that is just Xiaomi? Whats the difference?

Thanks

Edit: Also there's version 3 too?