I suggest you to give both a go and decide yourself which one you like more. (you can use one and install the other on a VM). Because you won't get a useful suggest because some will tell 7 is the best and will tell 8/8.1 is the best. because everyone has his own taste.
yes, yes, yes...like me here dual boot...wins 7 x64, wins 8.1.u 1 x64.. wins 8..on vm....
Ps:most apps/games run on XP..will runs just fine on windows 7....my vote agrree...