Nikko visit on a Fri. vs. Sat?

I am debating on whether to go to Nikko on 25 (Friday) or 26 (Saturday) of this month. It will be a day trip from Tokyo. Would the crowds be significantly less on Friday? If so, I think I will go on Friday. Is there any benefit to going Friday vs. Saturday or does it not matter?

Crowds will always be less on weekdays. Go Friday.

Almost all tourist spots in Japan are considerably more crowded on weekends (incl. Saturday) than weekdays. On weekdays, you have a higher chance of huge groups of schoolchildren "ruin" the atmosphere, though. During the autumn color season, I definitely recommend against visiting on Saturday if you visit the Okunikko region. But at other times of the year I personally don't think that Nikko feels too bad even when it is crowded.

If on a busy day you want to have fewer crowds, I recommend a visit to Taiyuin:
https://www.japan-guide.com/e/e3802.html

Don't expect Toshogu to be deserted.

Iroha-zaka on weekends during the fall foliage season will be congested.
https://www.japan-guide.com/e/e3816.html
On weekdays, there may be groups of children on school trips.
I went there when I was in 6th grade. (about 40 years ago)
https://gowithguide.com/en/blog/school-excursions-shugaku-ryoko-2358
On a school trip, I remember going to Toshogu Shrine, Kegon Falls (via Irohazaka), and Senjogahara.
So, I think those spots will be visited by students on school trips.
Possibly Ryuzu Falls and Yudaki Falls.
https://www.japan-guide.com/e/e3813.html
https://www.visitnikko.jp/en/spots/yudaki-falls/
Any other place would not be so crowded.

The autumn foliage season in Nikko is probably over by then, so it won't be as crowded as the foliage season.
https://koyo.walkerplus.com/list/ar0309/

I did not realize that you visit this November. Nikko is generally not very busy in late November (because the autumn color season has ended and winter is about to start). Especially if you go on the Friday, I would expect most spots to be relatively calm.