I don't fly AA, so I can't comment, but I can say that UA is awful. Every trip I've taken this year has had at least one segment with a substantial delay, including one flight from IST-EWR which was 4 hours late departing and then decided that since one toilet wasn't working, we'd overnight at Heathrow. Since you don't want to fly out of EWR, this isn't an issue, but flights in and out of EWR are almost always late. I'm still flying them because I'm close to 1MM and as soon as I get it, I'm switching to AA to see what that's like.