AVfile, sorry for late reply. I have been busy working with home-repairs.
I don't have photos, but have gone through the Screen, Video, and Picture Settings on both the TV and S790. I have used the recommended settings, have used the same settings for the HDMI as for the USB, and have tried every kind of variations. I have come to the following conclusion:
The S790 picture may have improved, because I think it looks good now. If I had never seen and compared the same film on both S790 and the TV USB, I would never have thought of it, and been content. The difference is very subtle. I don't think many people would even notice. The picture must be paused to see it. Most details are presented equally good, but when it comes down to very subtle color/shade variations, the S790 isn't quite able to transfer as good definition as the TV USB.
And I don't think it would make any difference if I bought another cheap new player like the S6500 instead. Reviews of S790 rate it with a very good picture, but not perfect. It is an inexpensive player, after all. So I guess there are more expensive players available to those willing to pay, that give an even better picture.