major handling difference...
although i havent ridden a yzf (or a yz for that matter) i read in a moto mag that the 2 strokes at rear wheel drive, and the 4-strokes are front wheel drive
meaning when your turning, you use more throttle control to turn than on a 4 stroke. this can be an advantage but only in great conditions, like really hard pack turns. If its sandy or muddy, it may become difficult, and the 2-strokes have the advantage.
I was really considering a 2001 yz250f for my next bike, but after hearing this, im moving more twards a yz125. I would ride both on both hard and soft courses if possible, if not try and get buddy-buddy with someone on more of a sandy course so you could witness a 4-stroke at its worst. Thats what i plan to do when the time comes.
After hearing this, i consider a 2-stroke the better all-around bike. This is just my opinion though.
later,
mxryder