Do not let the sound fool you, a 4 stroke pulls about 2000 more RPMS when compared to a 2 stroke in the same class. Ok, so a yz250, which is considered by many to be the best 250 ever made only pulls a pretty lame 9000 rpms. That is weak. But dont get me wrong the yz250 is still an awesome bike. Now a 450 will pull about 11000 RPMS. And you can def. feel it when you jump from one to the other. A 250f will pull about 13500 RPMS alot better than a 250 two stroke and better than a 125. You have been shown facts, if you still choose to ignore them then that is you stating that you do not mind being misinformed. And the weight difference is non existent on modern bikes. A 250f only weighs about 6 LBS more that a 125. And the greater inertia is already being addreses with machines like the husaberg FE 450 and more noticeably the 2010 YZ-450, which both have a rear tilting cylinder, although more extreme on the FE.