Well, the only Spanish food I know is Paella, which is delicious btw.
I'm Mexican so I can tell you that most of our dishes are fried, spicy and hot (specially hot, we love salsas and chili. I think that would be one difference. As I said before, I only know one Spanish dish, so I can't compare it with Mexican food.
Anyway, if you go to one of those Mexican restaurants, try pozole, mole or tacos! :D