Researching it seems the 5308CI uses a Realta chip, not a Faroudja. Is the Onkyo still a better way to go from a video standpoint?
The 5308Ci is $5200. The Onkyo is $1600 (or less) and the Rotel 1095 can be had for $1800 (or less) for a difference of at least $1800.
Is it worth $1800 to marginally improve upscaling on broadcast sources, which are of questionable quality to begin with? I don't think so. Besides, the difference will cover the cost and more of the Denon Blu-Ray player (with Realta) which can process video internally and pass the signal straight through the Onkyo. DVD and Blu-Ray quality should be stunning.
The big issue with broadcast sources is compression artifacts, like mosquito noise and block artifacts, neither of which are handled by either the Denon or Onkyo from what I can see. If your father has complaints about the image of his broadcast sources, there is always the option of adding an external compression artifact reducer like the
Algolith Flea. Get the main system hooked up first then see if there are any complaints about broadcast video. If there are, then check out the Flea.