Motorcycle question? yz 125 or kx 250?

i at age 15 got a crf 150 trail bike and it was a great beginner bike. 5 years later i decided to sale the bike and move up. i basically would like advice on what size bike to get. i was originally thinking on a yz 125 but found a great kx 250 that is slightly used but a great bike and the much cheaper price would is a huge incentive to lean towards the 250. i'm only a little concerned that the 250 may be a little too much bike for me. i've ridden my dad's 200cc and a yz 125 and felt comfortable on both. for just a little additional info i'm 5'8" and about 170lbs. so which should i go for.