In addition to the very valid counterpoints listed here, I think its worth noting the false dichotomy of the question. If the initial assumption is that population is capped, that hasn't been borne out yet, and assuming we eventually leave Earth in a sustainable-habitats manner, doesn't have to ever hold true. If population-capping isn't the basis for your statement, then I don't see anything suggesting that the total number of people will be the same with and without cryonics.

We are not choosing between ourselves and future potential people - at the moment, we are simply choosing between possible-ourselves and definitely-not-ourselves existing in the future.