Are we talking about who would win in a fight between the two if that's the case than I'll try to give a good answer

First I don't think Ryougi being a higher level user of death perception really matters for this match up

"Shiki" both have an appropriate meaning. Consequently as a user of the mystic eyes of death perception it can be said she is several ranks higher than Tohno Shiki, who is pretty much her polar opposite.

since that only helps her deal with things like killing concepts more easily but this fight wont have anything like that going on this fight will come down to who's the more skilled in close combat

Ryougi is on same level of skill as Nanaya Shiki from melty blood the same Nanaya who easily killed Tohno in Kagetsu Tohya

This statement from the Tsukihime fourth character popularity poll outright said her skills match his

A character that seems have to have taken only the best parts of two characters: Tohno Shiki's Mystic Eyes of Death Perception and Nanaya Shiki's Nanaya Techniques. Every movement is high-spec, with no opening in either her offense or defense. However, attacks that do not use either her knife or her katana deal surprisingly low damage".- Character Introduction from Tsukihime's fourth Character Popularity Poll

Ryougi with her knife skills = Nanaya who beat Tohno Nanaya does not even have Death perception like Ryougi has he has pure eyes meaning that any damage Tohno gets from Ryougi going to be way worse than than what he got during his fight with nanaya

however in the Remake Tohno feat of killing Roa lower body from range might allow him to beat Ryougi

4Gamer:
The scene in that passageway was one of the scenes that I was thinking about while playing. By the way, Shiki was killing Lore's legs along with the corridor, but does that mean anything?

Mr. Nasu:
There is a proper meaning. Also, I think everyone has doubts that there is only one route for Arqueid ... but that too.

Since he would just stab a death point on the ground in order take her out however we don't really know how this ability works or if Tohno can do it whenever he wants without knowing this we can't say for sure if this is something he'd be able to pull off during their fight

So I'd give the win to Ryougi for being the more skilled fighter with better training since Tohno was not able to complete his training due to his family being killed of course if we talk about death which is a older Tohno from tsukihime 2 that would be a different story but this is just normal Tohno we are talking about

Ryougi has the clear advantage in practically everything. She's literally like a better version of him.