They are both fairly similar and the OEM versions are priced similarly. While I agree that the hardware will make a the bigger difference, 8 does feel a bit quicker to me. However it isn't really enough to make a decision on so in the end it's a personal preference. I actually found the metro ui to be useful in certain cases when it comes to looking things up, although learning the os still makes things a bit slow at first. And I like the new task manager that pops up in 8, it tells a fair bit more and organizes/presents things better than 7. But, like has been said, it's entirely a personal thing, try using 8 (for more than 10 minutes on some junky store laptop that you normally wouldn't touch with a 10 ft pole and see how you feel. In terms of gaming performance, short of certain game-specific incompatibilities, there is very little difference in performance, and those differences will likely go away in time as fixes are mad
2 big things I would consider are :
1) Windows 8.1 update comes out this year, and is supposed to address many annoyances people have had with the OS, research more for details
2) From the way I see it, Windows 8 is Microsoft's new OS, and short of some bizarre catastrophe is likely going to be the one they are sticking with and will probably be pouring their new innovations into. While support and development for 7 won't grind to halt, it wouldnt surprise me to see them focusing more on fixing and developing stuff related to 8 over 7 (short of their being some sort of major bug/issue with 7). And after they come out with some new sort of OS after 8, 8 will probably have support while 7 might not get much attention. Correct me if I'm wrong, but that was something I was thinking about when I was deciding