I have a 3.5 x 10 on my Omega. I have a fixed 4x on my Knight. I like that 3.5 x 10 a lot better. It's much, much easier to sight in at 100 yds with 10x vs 4x. I hunt with the scope turned on 6x, but I'll turn it up to scope out a deer in the brush, etc. so I know what I'm looking at. I have half a dozen 3.5 x 10 Leupold Vari XIII's. Love em, like having the same scope on all my hunting rigs, and find the higher power useful.
The only time you'll have trouble with a 9x is when you have it cranked all the way up and one walks under your tree. But that's trouble with a 3x, too!