Originally Posted by Dismount
I'd recommend guitar if you aren't interested in playing in a band (you'll get over that I'll wager) its a bit more rewarding. Way way back when I actually started on Bass, 7 foot of symphonic bass. When realized how close the instruments were related I switched to guitar.
Don't get me wrong bass is a LOT of fun to play, but three quarters of that is finding a hook between the drummer and the guitars (I really can't blindly following the rhythm guitarist, it drive me nuts).
Mechanically the bass is a bit easier, the guitar is physically easier.