The 250r is a two stroke, the 250f is a four stroke, This actually puts them in a different class. The 250f is in the same class as a 125 two stroke. A 450f would be in the same class as a 250 two stroke. So basically the 250f is quite a bit faster. The problem is that it takes a more experienced rider to tame a two stroke, so unless you are an experienced rider, the four stroke is a better choice because of the nature of the powerband.
