The free night certs are very likely Category 4. Whatever certs you get will likely have a six-month lifespan to them.

If you have good uses for the certs, then I'd consider the two signup offers roughly equal. I'd theoretically value 50,000 points + 1 free night greater than 30,000 points + 2 free nights since you obviously don't have to spend the points in six months, nor do you have to use them for single Category 4 nights.

But....if you do have a decent use in mind for the certs, it's probably not a big enough difference to worry about.

Are you sure the cards are otherwise identical? 5 pts/$ at Marriotts, one Category 5 Free Night on the anniversaries, etc. If everything else is equal, I'd opt for a lower annual fee over a higher one.