[Cry Me A River]

Immortality beats them all.

Particularly since anyplace super powers work, immortality gives you plenty of time to pick up new powers (find glowing meteors, ingest weird chemical concotions, hunt for magical/alien artifacts, learn obscure magical lore, etc)

If we're only getting the power for a week, immortality gives you the opportunity to do some crazily dangerous [censored] in the pursuit of more permanent super powers (glowing rocks and whatnot).

Alternately, "super-genius" also gives you the opportunity (even in a week) to come up with some long term super powers, even if just in the realm of super-science gadgets, weapons, armor, etc...