Hm. Muscle gain, If it would help things like the heart and stuff. I rarely do physical activity unless I am unloading a truck at work and whatnot. being able to build a little bit more muscle during those times might be overall a greater benefit to my health.
As for sleep...
5 hours would push me to the 7.5 hour minimum required for optimum performance, but 6 hours would boost me to 9, and anywhere after 9 is supposed to be "too much" sleep and have almost a negative effect. I would end up sleeping 6 or 6.5 hours and feeling like a sloth the next day. I guess I COULD just not sleep for that long, but who knows!