Service is nothing special. The CRJ is about the same level of comfort/discomfort on the two carriers and should only expect a basic bar service. If you're coming from DCA, I'd try to find a flight with the E75. The Air Canada E75 is very comfortable particularly in rows 12-16 with 34" pitch, the rest of the plane is 32" pitch which is better than UA's E-.

If you do try this out, make sure you leave enough time between flights as they will be on separate tickets if there are delays, which are not uncommon from the East coast. You have no protection on the next flight as they are separate bookings.

The good news is that as a *G you would have access to the ML Lounge which kicks any RCC. Out of DCA you may also have access to the DL lounge as AC's E's and SE's have access, again much better than an RCC.