I have ridden all of the Japanese 450 sport bikes, and I own an LT-R and a TRX. They are all great bikes, I think the biggest difference is going to be personal preferecnce. The YFZ may be the best all-around machine it handles great, but I personally don't like the way you sit on it. A longer steering stem would help that. The Kawi is a good machinge, doesn't feel as strong as the others IMO, but it is light handles well and had reverse. The Honda is the simplest, but that is not necessarily good. I is comfortable, handles well, the suspension is not as good as the others IMO. In my personal experience, between the two TRX's that I have worked on and been around, the wheel and axle bearings seem to wear faster and the rear axle lock nut is more likely to come loose. The LT-R is my personal fav, after I got used to the extra width and put a steering stabilizer on, it is fine in the woods. The frame is a bit heavy and bulletproof. With a few decent mods this machine hauls ass, and I have had no bearing or tie rod problems. With a + 1" steering stem and that big comfy seat it comes with, it is very comfy. The suspension is a bit stiff, but it has the longest travel of the 4 and with few adjustments it works great for me since I am a bit heavier than the target rider that they design the machines for. My only wish is that it was lighter. My friends and my own TRX's have had problems with breaking and loosing bolts in the subframe, and the main frame isn't as sturdy. On the positive side of that, the TRX's are noticeably lighter. The enginge is a little more accessible on the Honda, not a huge deal though. The Suzuki is fuel injected like the KFX, and I love being able to adjust my fuel mix by pushing a couple of buttons instead of changing jets. The TRX is the only one that uses a single cam, which is nice, makes valve adjustment easier and you only need to buy one cam instead of two. The tie rods on the Honda bend if you sneeze on them, between my friend and I, we have bent 3 tie rods in the last 2 years, where as, I have not bent one on my LT-R. On a more positive note, my Dad is a runs a shot-peen forming machine at Boeing, and he can straighten them out and they are much stronger after the shot-peening process. We have yet to bend one of the re-worked ones. Anyways, like I said, they are all good machines, I think each one could be the best choice for one person and the next guy might not like it at all.