It depends on want you want out of the bike. I run a 120 front and 140 rear. The larger tires track well while leaned over. No sketchiness when transitioning from side to side. As far as the Ninja's "flickability" goes, on these tires, the bike feels a slight bit heavier, so that it's not as quick to go over, but a slight adjustment of the riding style fixes that quickly. The bike actually feels like it has the handling of a bigger bike. With a little more width (both front and back) the bike leans over a tiny bit more. At higher speeds it's really stable but still easy to get over. Not a lot more force needed to get it to turn though. To me the 110's seemed to follow grooves too much when leaned over. Not so much with 120's
Keep in mind most 120's are designed for a bigger rim and most have different dimensions. The 120 I have was designed to fit a 2.75 in rim. Also there is very, very little space under the fender once you install one.
got my tires on, but now getting a total fluid flush, new o chain, new brake pads. my bike is gonna feel like a different bike when it comes out the shop, everything won't be done til sat (sigh) longest week EVER:bash3