7 was a facelift to Vista. It changed the control panels back to the dipshit XP-like way. That's not an improvement.

The kernel improvements landed in Vista. 7 inherited them. They "fixed" the driver support in Vista. 7 also inherited that.

I'm a Windows developer. Well, more so was during the release of Vista and 7 and certainly prior. Much less these days. I loved Vista. Worked flawlessly. I've also used 7 extensively. They're (near)exactly the same OS as far as the kernel and driver and API models.

Maybe as support for Vista ended and 7 got continued support. That's really the biggest difference, IMO.