I like both too and also my vote goes for Spiderman.

There are some pro's and con's i wont to list up.

Pro's and Con's for Spidey:
- His films are good, not the best because the stories are screwed up ( thinking of Gwen Stacy and Uncle Ben's Death for example.)
+ Spidey doesn't need a spideymobil or other vehicles to move to far places.
+ Spidey doesn't need weapons, he himself is a weapon.
+ Greatest Pro for me is, that Spidey has to work hard for his money.

Pro's and con's for Batman

- I like all of his movies but the problem is: you don't see the whole potential of batman. No regisseur succeeded in clarifying the hardness, the coolness and the sadness of "The Batman". Maybe thats why in every Movie there's another Batman.
+ He rocks! For a normal human without super powers he's great.
+ Looking at the outfits Batman rules! The dark outfit is great.
+ The background story is cooler and more tragic. Losing the parents in childhood is hard.
And Batman Begins was great but it can't reach the Spiderman movies.

At last i have to add. These two heroes are from total different worlds. Spidey is a mutant and has to fight other mutants with super powers. Batman is a normal guy that fights other normal guys.
But looking at the films, the spidey ones are better.