As mentioned in another recent thread, no cert is the be all end all. I'd say right now that NSCA is the gold standard, but even they need some work.
In the world of certs, NASM isn't bad. I'd say they're one of the tops, actually.
But since certs are near meaningless, my suggestion would be to get the one your gym advocates or likes.
If you're not going to be employed by a gym, go with NSCA. Or get both... NASM actually compliments NSCA quite well. Then understand that learning has only just begun.