So I got the D2 Air a week ago and really enjoyed it. I then saw where the updated X10 version was out so I exchanged my D2 Air for it.
So far I prefer the D2 Air over the X10.
The main D2 Air and X10 have almost the same Metar watch face, but the D2 Air has Yellow accent marking that make it easier to read. The X10 is all white.
The Time out on the D2 Air is better and only shows the hands and date where the X10 just looses the second hand.
The latest SW update on the X10 messed up the auto brightness.
The X10 does have the Voice Assistant button which works, but with a few second lag. It does allow you to make and receive calls and texts, but your phone has to be in Bluetooth range.
IDK, I think I prefer the D2 Air over the X10