I would advise panniers, since my backpack-carried laptop has served as crash padding for my shoulders before. :/ Instead of a fancy bag you can get a cushy laptop sleeve, and then any pannier or bag will do.
bkr
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-=- '05 Jamis Nova -=- '04 Fuji Absolute -=- '94 Trek 820 -=- '77 Schwinn Scrambler 36/36 -=-
Friends don't let friends use brifters.