You know, dyno charts can be all over the place. There are people on here who have dynoed their FZ6 with Laser Quads and have seen improvements.
I know that mine sure feels more powerful with them installed, and I definitely did not feel a power loss.
From what I recall on the "old" SBN board (around 2004 and in their archives now) was that the laser quad by itself gave about three or four horsepower and the cat eliminator adds about another four horsepower. I've attached the dyno graph from Foster Rad's site which shows a stock FZ6 versus just the laser Quad installed (no cat pipe).
Here's the page where I found the dyno chart:
LASER 'X-treme' Exhaust System tapered (4 x 70 mm) for the YAMAHA FZ6/S FAZER '04- | FosterRAD Laser Exhaust Systems
I too do not like the looks of exhausts which poke out of the back of the bike, but I do sort of like the new 2-brothers systems.
My laser quad looks awesome (in my opinion) and sounds great, without being obnoxiously loud. I would definitely go that route again for exhaust.