They are just slipons so power gains are all going to be so small it's not really a consideration IMHO. What I like about the R77's is that they fix a basic problem I have always had with the back end of the Busa. The "hump" makes the back end very heavy and it hangs out way past the rear wheel. It almost looks like the wheel is too far forward and not centered under the "fender". One way of fixing this is to do a 3-4" stretch, but let's just say I have a real allergy to stretching a bike that already has a wheel base approaching 60".
The Yoshi's solve this because 1) they are just the right length to hide the part of the wheel that looks to far forward and 2) they angle up slightly filling the void between the fender and the wheel. I didn't realize this when I bought the R77's but after hundreds of photos I realize what a great aesthetic fix the R77's are.
On top of that, the shape of the R77's really fits the Busa and the sound is polite but aggressive. The full header sounds even more snarly, but that means going to a single can which would reduce the aesthetic magic the R77's do for the Busa's booty.
Now I'm now saying the R77's are the only slipons that do this, I just really love their look and quality build. Besides Suzuki and Yoshimura go together like Ducati and Tamburini.