Macu09
If you still have the possibility i would start out on the M1 visa and do your private, then go home for christmas and change your visa to a J1 visa which gives you more time to get some practical job experience over here if you get a job and so on.
A lot of germans have done it, and a couple of others, its the way it gives you the most time here, but remember dec 31. is the last day you can apply for the J1 visa, so if you miss that date you will be in some trouble getting a new visa.
Good luck.