build Soren or raven

Raven is over all better since he's a hyper-offense hero but Soren is pretty handy with his debuffing tome Wind's Brand. It's whichever you're more in need of, like do you have enough green tomes or axes?

Soren if you want a heavy debuffing mage with ploys/chill, and raven if you need an absolute offensive monster. Depends on who you don't have in your team comp, really.

If you have a bunch of feathers, I'd say go for 5* merges. Much more arena score, and more potential than a 4*+10.

I'd say Soren he's a pretty versatile green mage, although I also have a bias toward him over Raven.

Soren makes for an amazing mixed phase. Mine tanks Reins AND B!Lyn's with his refined tome and he's +spd-def; It's rare to find a unit that can double him when buffed by adjacent allies so he can even serve as a decent blue (and sometimes green) melee tank.

Raven is a lovely hyper offensive, but he's very fragile and needs a lot of movement support. Fully built though, he can demolish just about everything... just don't let him get hit.

Ultimately I think it's dependant on your play style and the kind of team you want.