Footprint is more important. there was already a thread about this if you scroll down a little.
for example
5x1x2 = 75 gallon skinny long tank
my tank, 5x3x2 = 225 gallon super wide tank
both the above measurements are 5 foot long 2 foot tall tanks. so as you can see the footprint is far more important. If you have a 12" wide tank, with a 12" fish in there, the fish can only swim up and down pacing. this is very cruel. its why you can't keep oscars in a 55g tank. they need a larger footprint.
remember, wider is always better than taller. length and width are the footprint, which dictates what fish can live in there. the height is really only for asthetic purposes as fish don't swim vertically. the only benefit of a taller tank would be if you are keeping deep bodied fish like giant gourami.