Do you mean Windows 8? It isn't launched yet! And from what I've seen (I've downloaded the previews) I wouldn't touch it with a barge pole.
Assuming you mean Windows 7 then most people (including me) regard it as a significant improvement on Vista. There is a "Windows 7 compatibility tool" on the Microsoft web site (that might not be the exact name, so Google for it). You download that and run it, and it will warn you of potentially incompatible hardware and software. It's pretty conservative, and even things it warns you about often run OK on W7, so Google for info about anything doubtful.
Windows 7 64-bit will run on 4G of memory but I wouldn't recommend it on 2G - use the 32-bit version on the laptop and (I recommend) 64-bit on the 4G machine. I can't remember if you get both 32-bit and 64-bit versions when you buy W7, but check. In 4G memory, W7 is usually as fast as Vista. However, W7 on a 2G laptop may be slower than XP.
W7 Pro has virtually nothing for the home user over and above W7 Home Premium. If the offer is only for Pro then fine, but don't pay anything extra for Pro over Home Premium.