If frequent upgrades are your priority, then you should fly DL. Just don't be upset when your miles are not worth anything.

I don't think I've been on a CO plane with an F cabin yet this year, so I really couldn't tell you how my upgrades on CO compare to DL, although I can say that I almost always got upgrades on DL domestically.

The problem with DL is getting a C seat internationally was neigh impossible.


More generally, are people REGULARLY seeing these upgrades offered, or are we just dealing with a few anecdotal cases here?