Already has maxed Kiril, Gormek, Tiburtus, Sabina, Melendor and have a 60 Caedmon that i probably full ascend at some point.
Fact is that i give more importance to titans and events, so ideally Grimm would be better without a doubt.
I usually running Sonya only against Ares, but she can do the job even not maxed and pretty much the final ascension strengthen much more her tank asset.
But she has fast mana and single target huge shot special, so situationally having her in the event would be good.
I see some people running Caedmon this event and do pretty good, and she is rather similar.