I think overall Star is a much better alliance than OneWorld (particularly as BA has cut a number of routes), and that it serves many more destinations (with South America a notable exception). As for credit, I think most FTers would gripe most about the BA/AA no credit for TATL flights on the other rule. (This has not been much of an issue for me, as I'm a top tier member of both programs, but if I weren't, it would rankle). This COULD change IF they get ATI, but I think that's far from certain. The 25% mileage credit on BA cheap fares on other routes and reduced or no mileage credit on other OneWorld alliance members you raise is certainly an issue, but not, I think, peculiar to OneWorld. I remember getting heavily reduced or partial credit on SK and AC flights when I was a UA 1K; perhaps the difference is only one of degree: for flights with LH (the primary European carrier and big gun in the * Alliance), one gets full mileage credit, whereas in OneWorld, reduced or no mileage credit on many fares/routes is much more common?

In any event, having suffered through numerous connections flying ex-NYC in my UA years, I'd suggest that, IF you think you can make it to EXP, you make the switch to AA for its much better routing ex-DFW, its superb EXP desk, and its generally better UG program. If not, I'm not so sure: with so many EXP's in DFW, I think your UG chances may not be so great, and E- on AA after riding in UA's E+ is really not going to feel good.