Any real difference in using a 2019 Nvidia Shield as a server over a 2017 model?

To me, it doesn’t seem like it would make too much of a difference? Both are pro versions.

Newer Hardware, better hardware...a remote design that actualy is useable.
Has few more software features that the old one does not.
You can not buy new the old model, its not made anymore and it can loose support/updates anytime now and be full EOL.
Nothing more to say really.

If you can get the old one used dirt cheap, I would say it is still a good deal.

As a server either one works no real difference. Your post did say as a server not a Client. I recently set up an older one as a DVR Server ... serving up tuners and streams to ChannelsDVR EMBY and Plex

This is exactly the response I was looking for, thanks!

Not entirely true. The 2019 model has slightly better cpu and gpu. Slightly faster.
So, things like transcoding and comskip with have slightly better performance.

Personally, i prefer a Raspberry Pi4 for a server.