It depends on a lot of different factors. With your height and weight I would personally lean more towards the 400, because it may fit you a little better. But if you are new to riding a 250 would be a great bike to start on. I am the same build and had NO major complaints when I rode my friends 250 for a few hours. The 250 is a lot smaller than i am use to so it took me a little while to get the feel of a light agile bike. At the time i was riding a 1980 GS1100e which is a big heavy thing. I have never rode a 400 so I can not honestly say much about them.