It depends on which airline you fly more. The Mileage Plus cards don't offer Silver status, but do offer boarding group 2 and a free bag, which is basically Silver minus the upgrade opportunity (which is virtually zero for UA Silver).

You can look on this forum for commentary about those supposed "benefit" tickets on CM. I had a Banco General Connect Miles card for 5+ years, and tried to use those companion tickets and other things, the fare class necessary to use the benefit was either unavailable or more expensive than just buying two regular tickets. (Which is the same thing the poster above is saying.) I was very unimpressed with the CM card, but maybe because I was attributing all my CM flying to MileagePlus.