Evilswarm Ophion

From a gameplay perspective, I'd have to say Xander. Ryoma's niche is killing enemies as a front line unit. That's nice, but units like Coriin, Saizo, etc. can fill that niche just as well or better than Ryoma. Xander, on the other hand, provides the versatility of a mounted unit and shelter utility. He also acts as a defensive tank which is sorely needed in CQ around his join time.