My buddy rides an LTR and when I was looking for a new machine he tried to steer me in that direction. I have ridden his bike, and it is a great machine with tons of power, especially with the Yosh Cherry Bomb added. Where else can you get that kind of performance increase for $40. The problem I have with the LTR is the suspension. It is pretty stiff and tends to throw you around a little more than I would like. I am disabled (although you'd never know it when I ride) and when the bike starts to kick I find it hard to keep my center, and keep my feet planted on the pegs. I also find the controls are a bit awkward for a guy my size. Other than that, I think it is a great looking machine with power to spare.
In the end I choose the KFX mostly because of the reverse factor, and the looks. For trail riding reverse is a must. I never had it on my old quad (a Bombardier DS650), but now that I have it I'm never giving it up. The suspension on the KFX is nice and I find it a bit smoother than the LTR, but with that being said it still took some adjustments to get it there. Ergonomically I find my KFX much more comfortable than my buddy's LTR, but that could just be a matter of what I am used to. Power wise, I can't compare since his bike has a few mods and I haven't done mine yet, but I am convinced that after I install my new pipe, PCIII and open up the air flow I will beating him off the line, and all the way down the track.
I would say the LTR probably handles a little better than the KFX just because it is wider, and lower, if you can get past the stiffness in the front end. But they are both great handling machines that are relatively light and easy to throw around. With a few tweaks and adjustments, and maybe some aftermarket upgrades they both have the potential to turn on a dime and handle like their on rails.
The only complaints I have with my KFX is that the seat is a little hard and there is some vibration at high RPMs due to the alluminum frame. Both of these issues can be easy handled with a few after market purchases.
I did notice some hard starting issues through the winter when it was a little colder, but it wasn't so much a starting issue. It was more of an idling issue. She always fires right up, but without a choke or fast idle it can sometimes be tough to get the bike to idle when she's cold. But it just means keeping your thumb on the thottle a little for the first minute or two and after that you're good to go. But at the same time, I'm hoping with a little bit of tuning that will get better as well. And now that the weather is starting to warm up, the problem is gone. I can start it up and walk away with the motor purring like a kitten.
At the end of the day whichever machine you choose to buy is going to come down to your own personal preference, needs, and desires. But although for me the KFX was a better choice, I don't think you can go wrong with either of these two bikes.