One gets the impression that most of the fatalities occurred to people who were trapped or stayed below deck for one reason or another. Percentage wise, most of the passengers did evacuate successfully. It doesn't seem that leaving the ship, once you had reached an open deck, was the issue.

Life vests in the US are supposed to have 20 pounds or more of buoyancy and are able to turn a adult, floating face down, over and support them.

I would be very cautious about leaping fifty feet (or even a shorter distance) into unknown water, especially in the dark. It would be just my luck to hit a rock, which at that distance would likely result in a serious injury or worse.