Well, finally something I can have some real input on. I have a 2008 Hayabusa with the PCV, Autotune, and Two brothers dual slip-ons. I have a sport touring windscreen and helibars. I have a custom seat that drops my seating area 1.5" inches or so they say. I have aftermarket levers.
My buddy has a 2008 ZX14 with the same mods as mine. He has the risers and a sport touring windscreen also. Muzzy Exhaust, PCV, and Autotune, plus aftermarket air filter.
We have traded bikes several times back to back on various rides. I wouldn't say I have the greatest experience, but have some real seat time.
The ZX14 setup that way is definitely more comfortable to ride. I like how the clutch and the shifter is so smooth and effortless. The throttle just feels so much more smooth in my hand, very light and easy to spin the throttle in hand. His sport touring windscreen is taller and blocks much more wind. His headlights are far superior to the Busa in all aspects. He has much better night traveling lights. However, the ZX14 is hard to turn and couldn't get out of the way of itself and that can make you nervous is fast corners. The suspension is more Cadillac like or sport touring. The digital LCD dash is fantastic and shows MPG and all kinds of trip stuff. His brakes are 10 times better than mine, well not that much, but far superior. I might have to go with a brembo upgrade to get close. I changed rotors and put EBC pads in versus stock and barely noticed anything. If you grab a handful of the ZX14 chompers and you better hang on tight. I had to learn to not pull as hard. So much easier to change the oil and install frame sliders on the 14. That scores major points with me there; you don't have to open any of the fairings for most easy maintenance.
The Busa feels like it has much more bottom end and turns far better, plus the suspension is stiffer and a allows for a more sport car like feel. I like how the fairings stick out further on the Busa and blocks more wind. I prefer the peg location on the busa and feels more secure when hammering down on the throttle. Looks are a tough call, but I love the Orange busa, but I sure do love the 2009 Orange ZX14, but his is the flat black/burgundy with sparkly homo flames. That is probably my least favorite part. I also like the rear seat cowling on the busa and his has some plastic cover and it gets scratched easy.
The two are both nice bikes, but I am glad I went with the busa, but considering selling another bike of mine (600RR) to buy a 2009 ZX14 in Orange/Black. Why not just have both, right?
We have raced several times and it is pretty close, but I am lighter by weight and tend to pull out a little bit by 160.
Kevin