Power-difference between 2T 250cc engines/generations?

I have to agree with QOS. My dad's 05 KX250(still on the original crank) compared to my 05 YZ250(complete fresh oem rebuild) is a lot more of a light switch. It comes on hard and fast(explosive) where the YZ still had hit, but not like the KX. The YZ was way easier to ride right off the bat. Once I got comfortable on the KX at the 2 stroke nationals, it didn't bother me anymore. Practice was a bit of a shit show though

It was always my understanding that the KTM was faster if it had a pipe and silencer. My brother had a 2011 250SX with PC pipe and we did some testing at the dunes. Thing just out pulled my YZ uphill, we were hitting a 3rd gear step down out of a corner as fast as we could and both of us were going much farther on his SX.

I also thought that all of the 02+ CR250s were slow, I had an 03 and my YZ was much faster. Then tried oput an 05 one day and was similarly underwhelmed. Good chance that they might have just been jetted poorly though, that mikuni was hard to dial and I wasnt even trying back then.

^ 3G CRs do feel underwhelming if 1) you are expecting them to have the low-end snap of a 2G CR; 2) the RC cables are not properly adjusted; and/or 3) the carb is not properly jetted. On mine, I've taken care of #2 and #3 (yes, you still need to tinker with air screw for changing weather conditions,) and I have learned how to ride it. It's miles faster than the 2G motor (which was one of the, if not the, quickest 250s for its era) and has no trouble keeping up with other 250s on starts/long straights. I rode a '19 YZ last year and while the power was better down low, it did not have the mid to top of my '05, and I felt the front pushed in the turns (but admittedly the bike was not set up for my weight/ability).