Tho it's "apples and oranges", I think what's un-matched is United's CRJ550. For an aircraft of CRJ550 size, limiting seats to 50 passengers is a much more spacious experience.

DL's A220 was a lucky purchase for Delta. When originally marketed by Bombardier C Series, Delta snuck a steal of a deal for a struggling Canadian aircraft maker. I wouldn't necessarily credit Delta for investing in new aircraft, but really, it was DL trying to under price a failing Canadian Aircraft maker which DL later convinced Airbus in saving the order and purchasing 50.1% rights.

Jiburi