Whichever team makes the stadium work will move forward, so probably whichever one is furthest along will come out on top. They may both move forward, but that's not likely sustainable. The stadium issue is the only reason we don't have a team already. We don't have a good place to play soccer, meaning either the city chips in (cities do chip in for USL stadiums, often in hopes of moving up to MLS eventually) or it's private funding. And as we've seen, that's a long row to hoe.
More than that, location makes or breaks these things. Accessible stadiums in centralized urban areas tending to be the more successful ones. Land in the suburbs is cheaper and you can do more with it (training fields, etc.) but in the longer term, most fans just aren't driving out to the burbs for minor league soccer.
Oh, and the idea that soccer-specific stadiums are necessary for success is a canard. That doesn't play out in MLS and it won't play out in the lower levels. It's location, location, location.
