As someone with the 13, I would prefer the 6 slots on the 16 to the 4+headphone jack on the 13.
If you think that getting rid of the headphone jack would result in more slots, you're out of touch with reality. There would be an additional slot on the other side of the chassis where there is no headphone jack, so 5 overall. But there aren't. The headphone jack has absolutely nothing to do with the number of slots. Audio output is a tiny component.