I suppose no one counts the fact that most airlines have "standard" awards with no capacity controls at higher mileage levels than the lower mileage level awards.

UA is particularly good on non-Hawaii domestic awards because their standard award is 40,000 miles, whereas most other airlines require 50,000. Also, on UA if you book a standard award, the reservation is booked in Y, which means you get E+ seating even if you are not premier or for everyone in your party, even if they are not premier. Also, changes follow the same Y class unrestricted rules.