It is a good idea to get a fee waived card to see if you like it. I find UA miles difficult or expensive to use. I like the Chase Sapphire Reserve for the airport restaurant benefits with the Priority Pass membership it provides. I also second the comment on transferring points to Hyatt.

I have only used UR points once to book travel directly. It was an United flight because it took more points booking it on United.com comparing to using UR points to buy tickets. As I mentioned, United miles can be expensive to use.

The last point I would make is the potential earnings. Check the T&C on the UA card and see your potential earnings. If you get similar point/$ earnings, I would stay with SR because it is more flexible unless the free bag check and 2 United Club passes are important to you.