I'm looking to buy a Crumpler bag for my new 15" PB. Is a backpack style or a messenger style bag better? I travel occasionaly, but will mostly use the bag for school (PB, a few books, ect.) I'm short and am worried about getting a bag that is too big for me. Are messenger bags harder on your body (neck/shoulder ache, ect?) than a backpack? Thanks for replys in advance.