I agree that Delta is really good. Recently when I mailed them with paperwork for Austrian airlines flights, they credited it in about 6 weeks which is not bad. But it is a bit of hair splitting if Delta posts flight miles instantaneously, while if United posts the flights in 1-2 days. I can readily live with a 1 or 2 day lag. What needs to be improved is - credit for partners, credit for online surveys and bonuses (United is slow on these), and online award booking.

For me - paper statements are almost obsolete. With United, the paper statements sometimes contain more detail about the bonuses. If the online version had these, I would not even bother with the paper statements.