One startup at a time?
Mz: A) I would be concerned that the one with all the money will turn out to be a lot better at raising money than at creating something.  In the long run, you cannot borrow your way out of debt.  So if they can't produce something, they would eventually go bankrupt.B) If at all possible, in the same situation, I would try to spend a little time on each one and see if I could learn enough from each of them to figure out what is 'wrong' with each and try to make a more viable go of whichever one seems best for me.  They sound like each one has done one piece of it well and not the other.  It sounds like a unique opportunity to experience the two things first-hand and grow a unique knowledge-base, out of which something really viable is much more likely to be born in the future.