The problem between a modded 125 (139, 144, 175) is that although they make more peak hp than a 250F, they do it only in one spot. Using the graph in MxA as an example (and this is from memory so don't expect the numbers to be exact...), at 7000, a 250F is like 30 hp, while the 144 is at 17 hp (about the peak of an early '70's 175). The 250F numbers climb very slowly from there to 14000 rpm and peak at 35 hp but all that way they are +30 hp. The 144 slowly climbs until about 10000 when BAM! 38hp! to 11000 and sayonara.
To me, all that is very over simplified but Jeremy McGrath or Ricky Carmichael couldn't keep that 144 in such a narrow power band forever. I would gladly give up the 3 hp to have that power in a wider range (in an equal machine). It would allow a lesser rider to compete just that much more evenly, and in the hands of the really fast...makes it no contest. Of course, between the 2 and 4 strokes, there are other differences that all favor the 2 stroke, thus narrowing the gap further; weight, turning ability, braking, "snap", all are important parts to the equation.
So, what am I saying here? I know it sounds like I am making a case for the 4$ but I am not. I am just laying out the facts while not fanning the flames and name calling. The modern 4$ is a technical marvel. In no other sport can you buy the equivalent of an F1 car (back of the grid of course!) off the show room floor. But with that comes a price and that price is more parts to wear out, a much narrower tolerance for failure, and a much higher price tag. We all know that cc for cc, the 2T is a better deal, but under current AMA or FIM Pro rules (you can run the 144 in the FIM 250F class - there is no difference between pro and amateur), you can't beat the 250F.
