I'm going to chime in here and try not to make things more confusing. The Nambo is the perfect bike for someone who wants 450 power (read linear bottom to top) with 300 2T handling, this is not a wild MX power band. I personally love riding this bike for shorter periods, but it wears much more on me on longer rides. It comes down to the right tool for the right job, how much of the throttle do you really use? Anybody can get used to any bike, but who wants to skin a cat with a chainsaw? If you ride wide open stuff where you're constantly looking for "more" then maybe this bike is perfect, but if you ride tighter slower stuff where accurate throttle control is more important then I would suggest the 250. Body weight, strength, endurance and ability play a big part as well, but try paying attention to how much of the throttle you actually use before buying a new bike, you might be shocked. Not to say that the 250 is a slouch by any means, but you have the option to ride it lower in the power band where it will "tractor" all day or spin it up to really pick up the pace fast. I have "tractored" up plenty of big nasty hills on the 250, it just keeps going, no spinning, flipping, etc. Keep in mind I'm riding at about 170lbs without gear and like to ride slower, nastier stuff. Honestly, you can't really go wrong with either model, both are incredible bikes, just be honest with with yourself before you buy.
Wes.