The difference between high mounts and standards is mostly aesthetics.
As far as good slip-ons go, you should choose a pipe that appeals to you aesthetically (i.e. appearance-wise and sound-wise) because none of them provide great power benefits.
In terms of build quality and sound, you can't really beat Akrapovic, Yoshimura, and Micron. They all sound pretty similar, deep and not too loud.
I had an Akra on my R6, and I now have a titanium TRS Yosh on my R1. I went with te Yosh because of the fit and finish (very good details and quality), uniqueness of the tri-oval design, and the way that it complements the 2002 R1's lines.
Good luck.