Based on what little info you gave us on your travel, I'd agree with flysurfer above that MP may still be the best bet for you. I also agree that should UA liquidate, there will be status matches galore to be had (I'm not so confident about matches of mileage balances, though).

If you are very concerned about your miles, consider burning some of them.

With airlines in peril and programs in flux (look at what's been happening in the european programs over the last year plus), I've moved away from hoarding to burning... Just figure out what you'd want to do with your miles and keep your account at that level by balancing your earning/burning. With UA, for example, I like to have enough miles for two *A awards in F anywhere in the world. When my balance starts getting higher than that, I burn miles on upgrades, domestic trips for family/friends, expensive intra-European flights, etc..