Pretty much any non-canon ship versus any canon ship, though most of the ones I see are against either Usagi and Mamoru
I mean it’s a fact that Usagi showcased attraction to other people other than Mamoru in
all versions (besides maybe PGSM) and Mamoru had his own fair of suitors as well, if people prefer to ship either of them with their other options besides each other that’s their right and is just a preference in the end. (Especially considering how poorly the 90’s anime did the UsaMamo relationship to begin with)
Unless these are outright crack ships like say shipping 90’s anime Usagi with Yaten (or basically any Senshi whom she’s never expressed romantic interest in which is all of them in the 90’s anime besides Rei, Seiya and Haruka for a brief period of time when she first met her and thought she was a man) or Mamoru with Michiru you can’t definitively say UsaMamo is automatically more “canon.”
Technically any character who expresses a romantic attraction towards another character on-screen whether one-sided or mutual is just as canon as any other, the actual term you’re looking for here is
end-game. As in which of these canonically suggested relationships ends up being together at the end. 90’s anime SeiUsa or UsaRei isn’t any less canon just because Usagi’s end game is ultimately Mamoru, they’re all attractions that were shown to exist within the actual canon work itself and therefore have just as much validity and claim to the title of “canon” even if they weren’t
actually endgame. (I do agree though that it’s dumb af if anyone tries to make the argument that UsaMamo somehow
isn’t canon just because of the canonical existence of these alternative pairings. They are and always will be canon and end-game in all iterations due to the very nature of how this franchise is set up, that being said I won’t lie and say I wouldn’t mind a version that makes an unexpected swerve from the expected and pairs up Usagi with a
different character at the end.)
In the 90’s anime alone we have…
Canon through one-sided feelings from either party’s side:
Usagi
—
Motoki (pre-getting together with Mamoru)
Umino (again pre-UsaMamo)
Demande
Mamoru
—
En
Fish-Eye
Fiore (This one’s tricky to categorize as he exists in the same grey zone Rei did where it wasn’t reciprocated but didn’t seem outright
rejected either)
Mimette (unsure if I should count Esmeraude for this too since she did seem to be flirting with him but it could’ve been an objective commentary concerning his looks as well)
Saori
Chibi-Usa (As much as we might all hate it, yes unfortunately it’s still technically canon from Chibs side)
Canon through reciprocation:
Usagi
—
Rei
Ail
Seiya
Mamoru:
—
Both Rei and Fiore…
kinda.
Then on the Manga/Crystal side we have…
One sided:
Usagi
—
Seiya
Demande
Mamoru
—
Setsuna
Beryl
Chibi-Usa (unfortunately even
more overt here but thankfully still one-sided)
Nehellenia, maybe/possibly??? (That one comment she makes as she’s disintegrating)
Mutual:
Usagi
—
Haruka
Technically her entire Senshi team since they’re low-key treated as her entire harem in the manga, especially if you take the entire ending into account. (Though other than Haruka the only other two of her Senshi that Manga Usagi displays attraction to are Rei and Minako)
(lmao Mamoru doesn’t have anyone in the manga who he expresses a mutual interest towards
besides Usagi)
Even PGSM, though much more trimmed down for potential alternative suitors on both Usagi and Mamoru’s side still has Ami for Usagi (The actress for Ami was outright told to play her like she’s “a girl in love” towards Usagi so yes, Ami/Usagi is technically canon to the PGSM-verse though only one-sided from Ami’s side) and Hina and Beryl for Mamoru. (possibly PGSM Zoisite too??? He seemed awfully attached to his “Master” compared to all the other Shittenou, hell Kunzite’s whole reaction to Endymion’s supposed “betrayal” was like that of a spurned lover so they could
both be considered viable options though I wouldn’t consider either
outright canon)
or sometimes Haruka and Michiru (mostly their Crystal versions).
I mean Manga/Crystal Haruka is canonically romantically interested in Usagi that’s a fact, and on top of her getting absolutely no development, build-up and little screentime towards her relationship with Michiru you also get the strong vibe that she treats Michiru as mearly a consolation prize for the actual person she wants to be with which is her “Princess.” Between that and the blatant cheating she does on Michiru it should come as no surprise that fans aren’t too keen on Manga HaruMichi’s relationship, they’re written even worse than 90’s anime UsaMamo is. That being said, that again still doesn’t make them
not canon or endgame. Word of God Naoko herself confirmed many years ago that Haruka and Michiru are an official couple, they’re actually heavily implied to be married in the Manga/Crystal and are outright raising Hotaru together as her parents. Anyone attempting to deny their clearly spelled out relationship at this point is silly and a big possibility they themselves are just homophobic.
But just because something is canon and/or endgame doesn’t preclude it from being badly written, and I would argue both Manga/Crystal HaruMichi and 90’s anime UsaMamo (especially post Makai Tree) are just that, which is why people would prefer to ship them with any given alternatives.