This is something that every new guitarist needs to know. There's always some blowhard who says you can't have "tone" without playing massive cables. Full disclosure: I play 10s because that's what I prefer. I end up grabbing 9s too hard and pulling chords sharp. That's actually a technique problem more than anything else. No sense in trying massive strings when you are just starting out. Once you've played a bunch and built up finger strength and callouses, try whatever you like! Premier Guitar had an article on this a few years back:

http://www.premierguitar.com/article...g_Myths_Part_1

Obviously here I'm focusing on standard tuning or Eb. It's different if you're doing drop C or something crazy. Then 8s or 9s would be unplayably slack I would think.