Hmm....let me think about this!
Hello,
Ive never owned a F4 or a R6! But.....I have owned a F2 and an F3. I know the F4's are improved, but they dont feel anything like the R6 does. A few of my friends own R6's and I personally love them(since when I was bikeless, I would borrow them for days at a time). I can honestly say that I have never had any problems with the Honda Bikes, unlike the Ninja's Ive owned. But I really think you'll like the R6 better. I like it so much that I almost bought one when looking for my R1. And maybe its me, or Im not use to the R1, but I can wheelie alot better on the R6 compared to the R1 or other bikes Ive owned!
Hope this helps!
Regards
Shawn