well on the track the 2 stroke will beat the 4 stroke anyday. the only real reason they made a 4 stroke to race motocross is because 2 stroke polutes much more and uses more gas than the 4 stroke does. if ur looking for topend speed ove a long distance than a 4 stroke is ur best bet. the 250 2 stroke has less horsepower than the 125 2 stroke but the 125 2 stroke needs to have rings replaceds ever 150 hours or so but its a cheap and easy job you can take the bike apart and put it back together in about 30 min for each. you can do the whole job if you have a honer. whilke the 4 strokes rings last longer you have to take the whole bike in to have the valves looked at and filed down. i own a 2002 suzuki RM 125 i have raced many 250 4 strokes and have never lost my bike is all stock exept the pistion and i have never lost to a single one plus it is way more fun to ride with a powerband. but i guess you have to figure out which you feel better rideing on.