Mr KX125 Rider,
To answer your main question, Yes I have based my opinions on my own experience on both bikes. (Except for our freinds that have blown up their 250f's and weren't riding while they were saving up the $2500+ to fix it.) The two stroke is far, far superior when it has a fair comparison. You are comparing apples and oranges. Not only are you comparing a 125 to a 250, you are comparing vastly different years of bikes! There is no comparison between a 98 and lets say a 2005 and up. There are alot of variables involved when comparing motocross bikes. Rider ability, CC vs CC, Terrain (are they motocross bikes on a track which they were built for?), vintage vs vintage, chassis maintenance, chassis set up, engine maintenance, proper jetting, ect ect. I recommend that if you want to get away from that "slow, lazy turning", take that 98 kx125 to a turn track and practice, practice, practice. It will reward you with a heck of a good time and make you faster on what ever bike you decide to get.