I'm Platinum OnePass since its inception. Travel about 100,000 Elite miles per year, almost exclusively Y fares, in/out of IAH to the Northeast.

OnePass is consistently degrading its benefits, and therefore has me seriously considering getting comped on either AA or DL. Thought I'd ask a few questions of the experts:

1) For both AA and DL, what would be the equivalent to CO Plat?
2) Which is easier to get comped to the equivalent elite level?
3) The single most important benefit to me is availability of domestic upgrades to elites paying Y. How do AA and DL rank in that benefit? With CO its guaranteed unless sold out already.
4) The second most important benefit is mileage accrual. CO Plats get normal mileage plus additional 125%. AA? DL?
5) The third most important benefit (anal, I know) is availability of rewards - domestic coach, Europe business class, Hawaii business class/FC depending on config. Is there a clear winner between AA and DL here?

Thanks for your help. If I can ever answer any questions about CO, let me know.