For just a slip-on, I'd say go with whatever you like the looks of best. Check out Holeshot & Hindle, too.
Even in the
FULL-system shootout tests Fast Larry did a few years back, there was a small difference between 1st place Hindle and Yoshimura and Holeshot's old & new systems. If you're going racing, it might be important, but otherwise, not.
The Yosh Zyclone setups are some of the quietest, just a little quieter than the Holeshot "Street" core cans, but still sound nice when you whack the throttle hard.
My son has a Yosh TRS full-system on his 1G and it's not offensive... at least to me. You might wanna ask the neighbors in his apartment complex though.