If you had no other lenses, I would go with the 35 F2 if you think you'll need the extra stop of light and for it being smaller. If not, then the zoom would be more flexible for the wide angle to short telephoto. Just my two cents.. I prefer the 35 F2 for my walk-around lens and don't mind walking to get closer or farther from my subject. And I do a lot of available light photography. If you plan on using a flash, then the zoom may be more versatile as well.
+1 - If you shoot a lot of available light, then get the prime. If not, the Tamron is a good option. Keep in mind that the Tammy is a bit soft wide open - certainly the 35 f2 is going to be sharper at 2.8 than the Tammy. Both are quality lenses, though. It just depends on your needs and style.