Hello, new here, hope I can share some points. I climbed to the 1400s purely with Water and I'm currently climbing in another account with Dark (1200s right now, I have some IRL stuff that makes me climb pretty slowly, but I'll get there), so I do have a bit to say about both Urshifru forms, hahah.
I think one thing that really should be looked at when analysing both is what impact they have in their respective types and how much their absence would impact said types. Water was amazing with Urshifru-R: always one hit KOing Ferrothorn with Close Combat and having over 80% chance of two hit KOing Toxapex, two of the biggest Water road blockers, was huge and I think it really pushed Water, specially rain (for that sweet boost to Surging Strikes), over the edge. After the ban, Water is still easily top 3 in the current metagame, but the things that are supposed to somewhat check it, like the two aforementioned pokemon, can both do their job and be beaten by smart play. I don't see a reason for Fighting to ever run Urshifru-R instead of the Psychic immune one, so I guess I can skip that.
Speaking of Urshifru-R, I don't have much experience with Fighting, so I rather not talk about it. On Dark though, there's obvious great team support with Tyranitar and Grimmsnarl (dual screens + Taunt variant) offering plenty of ways to deal with Fairies, and Mandibuzz (which, assumingly, I haven't used much yet) offering Defog and a defensive pivot, though I don't feel Urshifru-R breaks any of the "bad" matchups for Dark: between Bisharp, Tyranitar, Hydreigon and screens from Grimmsnarl, Fairy is decently doable in my opinion; Bug is definitely harder, but I built my Tyranitar to specifically counter Volcarona (helps against some other stuff too which is great), so the rest of the matchup becomes pretty doable too (Hydreigon is also a lovely fellow with Flamethrower); Fighting, finally, is.... An autoloss, lol, at least in my experience. Urshifru-R is definitely great in all of those matchups, but, as I descibred, doesn't particularly break any of them (in favour of Dark). Its absence would definitely be felt in a lot of neutral matchups.
Hope I managed to make a point and didn't just chatter for 3 paragraphs :x. Cheers!