You don't really think Boeing and Airbus do the maintenance themselves, do you?

Northwest and Delta did maintenance in-house. The new combined Delta does their own maintenance for both Airbus and Boeing.

It's completely irrational and illogical to think that Boeing "by far makes superior planes". The IFE is strictly a decision of the airline ordering the planes and has nothing to do with whether a plane is "superior".

Expect to see Airbus aircraft at Delta for quite some time. Better get used to it...