For me, I live in NW NJ ... that means my only status has been with Continental and now United.
It basically doesn't matter what the other airlines offer .... Continental and United have such a strong presence at Newark that I'm basically beholden.
My customers are all over the country and it's a direct flight on United from EWR to every.single.one of their locations. Every one.
So I'm sure there are upsides to other programs, but I've never had - nor do I expect to have - an opportunity to explore anyone else.
United's my ride-or-die. And trust me, they know it ...