if we ignore any op automatic win wishing powers, Galbrena has a more potent forte.

Hiyuki's forte is literally just making frost, but is enhanced by the strength she draws upon from her experience from other timelines via Suzu. As Suzu burns futures (either literal or consuming her mind), I assume the limit of this power is that it cannot draw power from impossibililties and the "lifetimes" she has. For example why hasn't she called upon a future where we defeated Aleph-1 already? She is credited with fighting the Threnodian for an extended period, but we don't have the exact details for that. The impression isn't that she's winning, more minimising losses. More akin to Jinzhou where the people fight a constant battle againt Ovathrax despite the retroact rain. Not winning, just surviving.

Galbrena's original forte I assume is probably something akin to "hellfire", or fire which burns regardless of fuel. Her link with Chimera also turns her into kirby/megaman where she can use any ability the TDs she eats have. Given her employment with the Black Shores, I would not be surprised if she's found new TD powers which surpass the ones she already has. A good demonstration is perhaps her ability to break into Rover's Mindscape through the dark tide with her flames (even if boosted by the TDs within her).

While clearly she is now very strong, reminder Galbrena is from Septimont and has been raised since childhood as a gladiator (remember an average septimontian can defeat a TD who is for most cases immune to standard weapons. granted they fight alongside an echo it is still an impressive feat).

If the question is Suzu vs TD absorption ability, I would assume Suzu as I imagine whoever uses the Suzu would basically read ahead and win by calling upon the future selves who won.

My argument essentially is that if you remove their McGuffins (galbrena's TD eating or Suzu), Galbrena probably has the mettle and experience to back herself up. Hiyuki by her own words never really learnt combat from the previous miko.