Right on BB!~
I like 2 strokes better too, there a lot lighter for one and well the power is just so dam addictive! A 125 will be more like your YZ, a little soft down low but rev it and OMG!
A 250 will be a eye opener all the time. Definatly try as many out as you possibly can. If you can try to ride a Honda. There bikes are really good. IMO just a notch above the rest, but its a matter of what fits you the best.