So I ran some rough tests with Satori and certain spells. Satori had equipment that boosts Attack and Magic equally and was Strategist, so nothing favoured here.
Characters I checked out were: Tenshi, Reimu, Ran, Suika's "Gathering & Dissipating", Hina's "Ohgane's Fire" and Komachi's "Narrow Confines of Avici"
I tested those spells on the Floor 1 Kedamas, since they are neutral to all of them (except for Ohganes Fire, more on that later)
Mixed Satori with practically equal attacking stats:
Gathering & Dissipating (fully magical) was strongest by not much, with Confines (only Magic as well) as a close second but both did way more damage than the other spells.
Reimu's composite spells dealt high damage as well, but not as much.
Ran's and Tenshi's spells were decent but not really anything to speak of.
Ohgane's Fire was actually rather bad, given that it struck a weakness.
Magical Satori with about 50% more Magic, 50% less Attack
Gathering & Dissipating melts faces. Confines too, but slightly less.
YinYang Orb & Phantasy Seal dealt the same damage
Ran's En no Ozu was slightly stronger, FYT Laser and Princess Tenko as well (given, they are magic spells) and did quite good damage.
Ohgane's Fire of course was stronger as well and deals useable damage.
Tenshi's spells of course are weaker considering their physical nature.
Physical Satori with about 50% more Attack, 50% less Magic
Gathering/Dissipating and Confines much, much weaker.
Reimu's spells still same damage
En no Ozu slightly weaker, FYT L aser/Tenko weaker of course
Ohgane's Fire nothing to speak of
Tenshi's Spells quite strong.
Bottomline: Gathering & Dissipating & Narrow Confines of Avici are imho the most abuseable spells out of the ones I've tested (and I suppose out of all available spells) but the attacks of the rest of those characters are decent as well.
So if you just want straight up damage and have both Suika and Komachi or can guarantee that one of them is out whenever Satori is fielded then go and run a magic build on her. Otherwise I'll stick to mixed since both Confines and Mist gained only about a third increase in damage for me when switching to magic which then costs you the versatility from being able to use physical attacks properly.
But I'm quite surprised that Gathering/Dissipating actually has a higher formula than Confines. Maybe it was to be expected since Confines carries much more utility and is also a multi target attack instead of Row target.