8.1 got my vote. One you've replaced the default "apps" with your usual programs, you don't spend long on the start screen. I've found it very stable (well 8 was anyway), and a decent OS to use. Win 7 is the past.
Get 8.1. If he doesnt like it he can get a start menu after which all the new stuff can largely be ignored. The other thing is 8.1 will have pro level features for 7 home premium price. For me that alone is reason enough.
Having used 8.1 for a weekend (albeit at a LAN so not exactly normal use) I'd probably suggest going for it, since as others have said, it's highly unlikely they're going to go back style wise, so may as well start getting used to it, I use the start menu in the same way (press the windows key then type for what I want) mainly, so that's not too bad. There are still various niggles for me, but it's just a case of me needing to spend more time with it to get used to it etc, while I wouldn't say it's better it's probably not worse once the initial 'training' period has worn off.
Windows 8.1 is the best out of the 2, 8 took a bit of time to get use to but 8.1 is the better imo over 7.
Just remember that win8.1 is quite new and some games will have issues. This should be resolved withing 4-6 months as per normal timeframe. some older games will not be updated and might require work a rounds but those are mostly pre win7 games.
8.1 for me. Windows 8 was always stable but i didnt like the new start menu amongst other things. 8.1 is a lot easier to pick up.
