If Bitcoin was to go down, I would like if everyone turned to the POS. I mean, rafical change will be needed. Out of all the POS, my vote goes for NXT. Their hardworking community deserves the chance. Also they are the only one that keep delivering all the promised features. I do own some NXT, so I might be biased.
There's the issue of a tiny amount of people being in control of the supply of POS coins. Some have done a better job than others but a properly developed POW coin democratises it a bit. Having said that I don't think BTC qualifies for that either.