PPV's are not as good quality as renting the disks.
SD PPV's are never anamorphic, so if they are widescreen, then they are letterboxed, and thus the resolution is not as good as anamorphic DVD.
HD disks have much more bandwidth and resolution than HD-PPVs, so the quality is significantly better.
The point of PPV's is the convenience.
PS The Guide Info should say "HD" and/or "DD" and/or "Letterbox" which corresponds to your 3 concerns (There is no way to tell the difference between DD 2.0 and DD 5.1, but Dish generally gives you whatever they get from the studio.)