@ Aqed That would depend on your systems spec, because if you've got a good graphics card and plenty of memory then Windows 7 is better for gaming. The reason? Because Windows XP can't give you DirectX 11, so you're not getting everything out of your graphics card by using Windows XP.
I am using both and perhaps windows 8 RP as main. Also found problem like system hang, MS Office not responding, IE not working and compatibility issue with various sites especially where high resolution images etc. posted. but so far not found anything which makes windows 8 better than windows 7.
I am getting addiction to Windows 8. Even RP is buggy and does not represent RTM version truly, still I prefer to use it for productive environment. In Windows 8 RP, I am mostly using desktop environment, coz it feels faster and easy to navigate (especially File Explorer). I use Metro environment very rarely except great games from Store