Which one should I buy Okay, so I've done a bit more reading than that...but I have some questions now that I've done the reading. First, myself. Im lightweight at 5'8'' 120lbs. I would rate my skill as beginner, I've rode for a good part of my life, but only chasing cows (ranching, fun) and in some undeveloped property working on my balance in sandy conditions as well as rock and muddy (deep mud!) in some swampy areas. My currently bike is a KLX250S (292lbs) thats really under powered. I have started a track that can travel the perimeter of about 30 acres, that Im riding to hone my skills. I also can ride on a home built MX style course, really Im looking to ride my bike a lot more in any conditions (Im a sled head) from the sandy trail, to the swampy mud bogs and take the MX tracks when I get a chance. I also want to dual sport it up (KLX gave me bad habits) to commute to work. Now, for things I understand: 250F more nimble, light, better for tight tracks. Be nice for chasing cows, they can turn on a dime and I need to as well. my KLX can out run a cow so Im sure a 250F can too. Probably suit my skill level on most terrain. The 450F is nice for the straight aways, dunes, and street. It is heavier, but still lighter than my KLX. Gobs more power too. Things I am not sure about (and why Im here groveling for answers) At my weight, will the 250F be sufficient on the street? I ride about a 4 mile round trip to work (90% of the commuting) and no farther to get to a majority of the destinations on the bike. I do ride some longer trails, gravel roads that are nice and open, probably 50-60 mile trips. If the 250f is not up to hauling me on the street, would the 450f be tame enough for me to come to terms, and be able to hone my skills sufficiently? Im used to a sled thats got some power (140HP) but I know thats a little bit different that on a bike. Again, I am used to getting wallowed around by the heavyweight KLX, so I question if I would notice how 'heavy' the 450F is in the tight sections. Anyways, I hope my question is a little more specific than the stock "250vs450 debate. I would probably be more apt to give up tight trail performance to gain (slight) valve train reliability and a more comfortable trail ride.