I believe Justinator tried them both and said fit, finish, quietness goes to the PEFI, however performance goes to the TD SQ, albeit may be a tad louder. I guess it depends on what means more to you, performance or quietness. If you ride alone, the PEFI is the ticket, if you wanna start bitch slapping people on the lake, you may want to reconsider!! Just my opinion....
I've got a 2.5 SQ on my SRX, and at low throttle, trail riding speeds, I don't notice the sound at all. It is a little louder than stock, but I really don't notice it.....may be I'm half deaf, I don't know. At WOT it opens up and flows, hence it is definitely louder than stock. At full whack, it has a nice roar, and you can tell there are a few hundred rampaging ponies that just broke out of the gate and wanna get some!!
I have an RTX with stock muffler tunes, and although quieter, I don't really hear an exhaust note. Strangely, I just hear air rushing out of it. Although quiet, it seems to generate a lot more under hood heat, which I'm not crazy about.
I've also tried the stock mod muffler, which flows slightly better than the stock muffler, is a little louder, but quieter than the SQ 2.5. I would rate it middle of the road, as it did not perform like the SQ 2.5, but a hair better than the stock muffler. IMO and knowing what I know now....I'd do one or the other, either SM or SQ 2.5!
Years ago, I ran a Turboflow 2.5. This was much louder than the SQ 2.5 and drove me crazy, but I would put it on when running with the boys and needed every stitch of power available. One night while out on a solo trail ride, I met up with a big cat who had been handing me my a$$ all winter. I was wearing that SQ 2.5 and thought, great I'm really gonna look at tail lights now. To my surprise, the mighty winder was able to claw its way to the front, and it did so quietly!! I never put that turboflow on again!!
I stand by my opinion....bang for the buck when comparing noise and power......nothing beats an SQ 2.5!!