Referring to the 2006 450s form Suzuki, Honda, and Yamaha I would say the LTR is the best. Now Im talking in stock form. A stock YFZ is better than a stock 450R, but the 450R has more potential than the YFZ when it is turned into an all out racer. Just look at the professional point standings, the top 10 pros are all riding either Suzukis or Hondas, at least in profesional motocross. Not a single Yamaha, with the exception of Bill Balance in the GNCC, and I would credit his sucess more upon his skill than the YFZ he is riding. Now when it comes up to a full race LTR450 or TRX450R I would say its a toss up they are to close to call. For 2007s on the otherhand it looks like Honda left the 450R relatively unchanged except for some cool new color schemes. I would say that was a mistake, Honda will quickly be left in the dust by Suzuki, and perhaps Kawasaki for not upgrading there quad. Yamaha also made the mistake of not adding any major updates to catch up with the LTR, although they do have some special edition models that may do fairly well. Still I think the YFZs will not do to well against the LTRs, and KFXs. It looks like Kawasaki is going for the throat with the KFX450, considering how it is by far the lightest of the four, it has EFI, and the fact that it is only an inch shy from being as wide as the LTR. Not to mention electric starting and reverse, I think the KFX will excell in both MX and CC. The only potential problem I can see is in the durability of the frame, I don't think aluminim will hold up as well when put through the rigors of racing (but who knows?). So then were does the LTR stand? Well as of now Suzuki has not released any information on the 2007 R450, which hopefully means they are updating it to stay ahead of its compition. If I were to guess I would say Suzuki would add a little more power to the smooth yet dull engine, aswell as do a little more fine tuning on the suspension, and lastly perhaps shed a few pounds seeing as how it is currently the heaviest of the four. So in conclusion I predict that the LTR450 and the KFX450 will be pretty close, but I think Suzuki should barely come out ahead. Honda and Yamaha on the otherhand will be left behind because they did not choose to update their quads to stay competative with Suzuki and Kawasaki. But thats just my opinion.