I have played both.
Drums are awesome......
PROS: great stress reliever, always in demand by other musicians
CONS: will annoy your family and neighbors, almosts needs it own room to isolate noise, is hella espensive, buying sticks and heads never ends if you actually PLAY your drums, you will soon think nothing of spending 200 bucks on a new crash cymbal when you already have THREE of them, they are not very portable and require a huge car or truck/van/suv to really get them around, playing by yourself gets boring after a while and you feel dependant upon finding jam mates which can be a pain.
Guitar PROS: Very portable, very gradual learning curve- you can be playing your favorite song in some fashion within the first few months very likely. Variety- you can play acoustic, electric lead or blues, rhythm, noodly jazz. You are actually making MUSIC and not just beats. Very portable- can you say camping, tailgating, sitting on your patio playing music. You can be your own musical accompanient if you wish to sing and write music.
CONS: You have to constantly tune, and deal with wankers wanting to touch your sweet guitar (mine are very precious to me), searching for the right amp/fx pedal/ brand of strings which is a never ending experiment that you will never find contentment in, and put up with people asking you to play stairway to heaven/enter sandman/their favorite song and acting suprised you don't know it.
I don't plkay drums anymore but wish I could have my old set back, but I never gave up playing electric and acoustic guitar.