I had the same choice to make a few weeks ago. I chose united for a few reasons

-united offered a class three weeks from CJO (DL is 16+ weeks(
-I live near a junior UAL base
-united has hired less in the past 5 years than delta
-united has more retirements over the next 5 years
- full pay in training at United vs DL 5000$ish training pay
-a ton more WB flying if that’s you’re thing

pros for DL
-profit sharing eligibility within first year
-no probation for upgrade
-generally has better finances than the other legacies


I didn’t include all the pros and cons but those are the ones that stood out to me. There’s a ton of threads with this specific question from past years, it has a lot of good Information. Try searching those for better answers. I It’s pretty hard to ask for advice on an online forum (not just APC) and not get some snarky comments. The position to be able to choose between the top legacies is amazing. I wish you the best of luck!