Hi, I have recently got a Sony BD Player ( It was cheap, shop closing) So I tried this exact experiment.
I use very good quality Scarte lead and HDMI Lead.
My Pioneer 50" is a great TV and I am a good distance away 3.5 mtrs ish.
On SD DVD via Sony or 596 I cant see any much differance. The 596 is great and if I find the audio is better, I suspect it will be, I will continue to use it for DVD Music discs.
The 596 cant play Bluray discs as you know but I cant see much improvement even then with Bluray.
Perhaps I would notice more if I had a Bigger screen or sat very close to my TV. But I dont!!
I contend that S vid (F80) and Scart or Component done well is probably better than HDMI done cheaply. Ultimatly Bluray should be better due to the technology but in my circumstance, I am not convinced.
I still wont buy over priced Bluray discs over cheap DVD's unless the content is somthing very special to me. Then I may buy both to give me playing options.
596 is a great CD spinner too. Chris smile

No 18 in the Hall of fame smile I have simple tastes; I am content to settle for the best:
GIK monster bass panels, rear wall. QNAP TVS 471i3. Roon into DSP5200SE via 210/ 218 zone... Explorer 2. Bluesound Pulse 2, Mini & Flex. 596v1, 518, Foxsat HD, Sony BDP, Pioneer 5090, 2 Chromecast's for LRB videos. MS200 to F80 for a Roon zone