I like and use both. I had no problems running windows 8 on my EEE PC 900HA, which only has the 1.6ghz atom, 2gb ram, and intel gma950. It's just as fast as Windows 7, if not slightly faster, since it seems to be a little better on resources (lower ram usage and less cpu usage). I also found that even without video drivers installed, windows 8's version of aero was still functioned solely on cpu power, and it still worked quite well! Stuck at 800x600 of course though =P.
To decide it depends on what you're like. If you want upgraded windows features like new task manager, windows backup, start "menu" etc. and are willing to relearn how to use it a little bit, then get Windows 8. If you don't like change and can't stand relearning new things get Windows 7.
Or try both as suggested, it's highly recommended if you can.