I just feel like with the start-up of pound blitz, it's dangerous. It's predictable too, as pound blitz is one of the few reliable kill options. Up-throw can be DI'd, so it isn't safe. Its not too great out of shield, because its weaker than normal rest. It can be hit after up-tilt, but again that's only if there is no DI, which isn't common. Rest is good out of shield, it has rising Dair, and if you need a late percent kill like what leaping rest provides, jab SH rest works on all of the cast, due to it lifting them off the ground, and then the landing lag (be careful this doesn't work on low percents because they stay on the ground).
Rest is more powerful, more combos, and more applications. The only thing that leaping rest has over rest is that it can recover on delfino, halberd, wuhu, and skyloft. And even that is super punishable xD