Despite everyone's hopes, the Delta/United merger is a bust! Miles/segments flown on one do not count toward elite status on the other, so I wouldn't count on it helping you reach elite status. All you can do now is earn miles from one partner in the other's frequent flyer program, nothing more. It's just like hotel or car rental miles though, they don't count toward qualification.

That said, to still answer your question, I personally prefer Delta, but that's partly because of location!

Things I like about Delta over United:

* Best web based milage tracking in the business (the miles are in your account when you land and you can see them on the web or by phone).

* Electronic segment upgrades, no paper to wait for in the mail or lose.

* Don't skimp on the first class seats. Lots of 757's (24 seats), 767's (18-24 seats), new 737's (16 seats), etc. United scares me with their 8 F seats on some of their newer planes (Airbus)!

Big drawback with Delta:

* You can't upgrade the L class fares (cheap advance purchase fares).