Well lets look at all the bikes:
the 250f is a 4 stroke dirtbike which means it will require less maintenance but it will be much more expensive. but it will be friendly with you cause they are user friendly. plus you wont have to mix oil with gas
now the yz 125
its a two stroke so more maintenance but cheaper. you have to premix oil and gas .... then i think is way more fun because when you are riding two stroke the bike has a powerband, etc.. is way more fun ... but with a error it wont end good . im not talking a little error but you have to be carull with the throttle.
i would go with the yz 125 i dont care for premixing oil and gas and im a extreme person so just choose what your going to do .
the yz 125 has more revving than the 250f but just revving the 250f has more torque... so yz 125 was made especially for fast... so its your choice really im about to buy a 125 because they are more fun and cheaper to maintain, who really cares of mixing oil and gas hope you get your answer fun... you cant get wrong with neither of them they are great all around bikes. just consider the other things...
