I'm not familiar with vinyl pools, they are not popular around here. However I can tell you that both the Polaris and the SWG are way overpriced. You can get a Jandy SWG for $850 on-line and the Polaris 380 with booster pump is still under $800. I would pass on the safety cover also, I think a fence is a lot safer.

As for the builders, I would call several references and have a look at their pools. Ask about their post-purchase experience as well as their construction. Get references from several timeframes. Preferable some from 5-6+ years ago and some from last summer.