Agreed. If you're seeing a noticable perceptual difference between your 1080i DISH picture and a 1080p BluRay picture then there must be some settings that are wrong, or you're double-scaling the image.
Apart from the 1920 v. 1440 issue, a 1080i60 picture should have almost the exact same amount of visual information as a 1080p24 signal.
The big difference is in the CONTENT itself, not the delivery method. DVD authors have the luxury of time to master the information properly to optimize the mpeg compression and take full advantage of the bandwidth at their disposal. Television broadcasters inefficiently mpeg compress that stuff on the fly, that may be why you percieve a difference. Changing the television broadcast process from 1080i to 1080p over the entire path from camera to display won't fix that.