What if any performance benfits could i gain from upgrading Sony BDP-S370 to the new S790? Thanks

If the picture is different using HDMI then there's a problem somewhere(if we are talking blue rays). I still use my PS3 after experimenting with standalone and the only benefit was a bit less fan noise.

In the end, when watching a blue ray, you are transporting a digital signal from the disk to the TV. If something is different, then something is wrong.

Analogue and DVD may differ of course.

The PS3 does not create as clear a picture as my Sony. It's not bad by any means, but there is a lot of electronics and processing, not to mention heat going on in a very small box so extra picture noise is almost a given. Again with HDMI's i can see a difference, but im not saying 'more expensive' is better. Keeping noise out matters most to me. On a PJ slight differences can be highly visible. Also some Blu Ray players process the picture differently using varying chip sets and software. That is where the difference comes. If it doesn't 'pull' all the clean data from a disc that it can then it isn't going to throw it out on the screen.

This is what a reviewer says:

A well mastered and transferred Blu-ray will look excellent without any help from backdoor processing and it’s perhaps ironic we can almost best rely on a budget player to deliver the information unfettered. More expensive players tend to have more options for image manipulation and the processing grunt required to do so.