In my opinion, it depends on how you value frequent flyer status benefits vs. award ticket redemption. There are other *A programs that are much easier to reach & retain Star Alliance Gold status in, but in general they are also much worse for redeeming award tickets.

It also matters whether your expected usage of award tickets is mostly domestic/NA or whether you will potentially use things like the mini-RTW which despite devaluation remains one of the best deals going in any FF program for redemption. The trouble is some people will pitch Aeroplan talking about the CPM they get redeeming mini-RTW in F but the person they are pitching it to just wants to fly to Goose Bay to see grandma.

United is a good compromise program that will get you *G benefits as well as a decent award chart, but IMO if you are going to fly mostly AC metal then AC E50 is worth it for the upgrade credits - if you fly the right fares/routes to use them.