Personally, I don't find UA very appealing and feel they are noticeably inferior in-flight and in terms of service to both AA and DL. Given, as well, your preference to avoid EWR, I just don't see them as overly compelling.
AA is fine, though, and some things like their domestic F product can be a bit better than DL. But, in general, I find DL service to be superior, if not that superior. AA still does the sticker-based upgrades for those less than 100k miles, which can be annoying, but others feel that allows for better, targeted upgrade strategies. The bigger downside would be that I don't think you will be able to get to MEM or MCI without connecting.