Well Rhys > Soren should be one to look at, but it merely boils down to healing vs. sometimes doubling the slowass enemies and slightly better durability. Soren requires EXP in order to even come close to being a healer and, on top of that, could cost us a crown within the process.
She can be Shoved easier as well (IIRC, Rolf and Soren are two who can Shove Mist but not Rhys, and a few more later joiners as well). It makes her much more reliable in a pinch.
Rhys is still shovable by a bunch of people. The list is right here:
- Nephenee
- Brom
- Lethe (Transformed)
- Mordecai (+ he can smite)
- Ike
- Boyd
- Shinon
- Gatrie
- Mia
- Ranulf
- Kyza
- Raisin
- Janaff (Transformed)
- Ulki
That's like... 80% of the GMs cast right there. The only ones who technically can't are:
- Soren
- Mist
- Rolf
- Untransformed Lethe + Lyre
- Untransformed Janaff
Pretty much the bottom of the barrel units here (barring Janaff who's likely staying transformed). The being easier to shove likely lasts for 2 chapters at best (3-P and 3-1) where it's just Soren and Rolf.
Also better affinity (Def >>> Hit) and she avoids getting doubled sooner.
Fire may not be the best, but Hit is still welcome. We can still be thrown into Worst Biorhythm and the opponent could be... well, anywhere else. Gatrie w/Steel Poleaxe manages 103 Hit, 118 with Ike's Authority. Under worse biorhythm conditions and units usually average ~50 Avoid, Gatrie can fall slightly over the 50% chance to hit something. With C Rhys in effect, this at least changes to 58%. B, eventually, could change it to 63. Now I'm not saying Gatrie wants a Rhys support and vice-versa, but the extra accuracy can still be a slight advantage to have.
and she avoids getting doubled sooner.
I do have to agree with Paperblade here: unless we pour massive favoritism it isn't going to happen lickity split unless we have Transfers on her, which the one I'm arguing doesn't.