Choosing between Delta and United

What flyers who have used both Delta and United actually say about hub fit, delays and cancellations, and loyalty programs, beyond either airline's own marketing.

• Delta or United: what do flyers say? Delta, for most flyers.
• How do Delta and United compare on delays and cancellations? Delta's on-time record is better, but United's close.
• What do frequent flyers wish they'd known before picking a loyalty program? Pick one program and stick with it.

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