I only have a pinch over 100,000 lifetime miles on UA but after reading some of the posts here on this thread I'm somewhat glad I went with DL when trying to decide which of the many airlines I use as a military member to use for my FFP.
As a serious rookie at ALL of this I will reach Silver Medallion right around June 22nd, then I'll experience just a sampling of what some on this board are used to, although my military status helps with seat assignments when in uniform. . . Note: I don't wear the uniform unless going from work to airport, plus the bag is lighter without boots!
Aloha!