I can't tell you much about the new 250, but I do know the 225 has been out for years (if not decades), and has been a super reliable bike. The 6 speed is a plus.
I haven't heard much about the new 250's, but I did check one out today at BSA in Marquette, and they look pretty sharp. If they are like all other Yamaha products, should be reliable.
I would go for the 250 as it is a new design and as your skills progress, you will be able to take advantage of that extra 25cc's!
Come join the Yooper thread in the regional forum...