Cannot Tell the Difference with Panasonic ES-10 NR on/off
 

Two screenshots are posted here of a paused frame from a video that was being captured from a JVC SR-VS30 and being passed through a Panasonic ES-10:
https://imgur.com/a/xQokH

One has NR on and the other does not. I honestly don't remember which one is which, but I cannot tell the difference.

I'm curious if it is just me, or the video experts here on this forum are also unable to tell.

There's no way to tell the difference from a paused frame, a still mage, or a frame as seen through a media player instead of a direct frame copy. You appear to have disturbingly soft video playback, if all you consider are the posted images. Why are you capturing at 640x480 (or has this image been resized by your video player, which would be another reason your posted test is invalid).

Next time, create your images directly from the video using something like VirtualDub's ability to copy unaltered frames directly from the original video. And when you're checking for noise, use moving video rather than stills. I still see a lot of bad noise remnants in both images and detail lost and distorted through jpg compression. Use lossless png next time. IS this tape a 6-hour extended play recording played thrugh a JVC with JVC noise reduction engaged? The detail is really poor. Leaving the Panansonic NR on causes motion smearing and posterization effects, but your images are so processed and multi-generational that it's difficult to detect differences.

By the way, you should post images directly to the forum. As soon as your images are removed from the offsite location, your forum post and your question will be meaningless.

The original video is captured from film onto VHS, so that is probably why it appears soft. And this is literally a screenshot of Vidi, so that probably explains why it looks compressed.

Still, I was expecting there to be a noticeable difference in the actual video as it played in the preview and there was not.

What would I look for?

This is mostly for curiosity. I understand that the general advice from this forum is to not use NR from the Panasonic.

To me, it seems like if there is any difference at all, it is extremely subtle.

The question can't be answered from the images. And you should submit moving video for questions about noise and NR filters. The results will vary frame by frame.