Not much comparison on low end power between the 200 and 250 exc 2 stroke versus the rfs or sxf 250 4 stroke. The 4 strokes make their power by reving. The 2 stroke have much more down low although the power curve is steeper with the 2 stroke. The 06 250xc or xcw with the 36 carb has a lot of torque. 04 and 05 really benefit from a 2 ring sx piston and head which is less than a typical aftermarket pipe. 200's with a moose spacer or 06 spec ktm intake spacer, and 06 spec pipe do pretty well after jetting is sorted out. For maximum low end a 300 will be lighter than a 250rfs or sxf.