Hello. You used to know me as Skippy the Great on Marriland.
Are you specifically asking the question about Snorlax, or do you also plan on breeding one in Gen 5?
If you plan on breeding (and care about this) I could send you Miltonic's Snorlax if you don't have it, It has Curse, and Selfdestruct (Selfdestruct is breedable in Gen 5).
As far as your actual question about Fire Punch, without it, you may loose the ability to hit quite a few UU theats on the switch you might want to KO. Bisharp, Klinklang, and Cobalion immediately come to mind. Without Fire Punch, E-quake is a must (IMO). No need to worry aboth hitting levitating Steels in UU though.
Fire Punch would probably only be a better option if you are either teamed with, or against Vulpix/Sun teams.