5* help

Who should I upgrade to 5*s:
Camus or Nowi (+SPD, -RES)

Both are really good choices and SI is easy to obtain for them, but....
Basically my defence team is utter crap (Celica, Hector, B. Cordelia, Ninian), good heroes but just not for defense. So in here, Nowi would be a better choice.
In the other hand, I've been wanting to make a Calvary team consisting of Xander and Camus and the movements would be awesome and just plain fun to play as well as a completely different defensive team.
I'm unable to play much often and F2P (sometimes) so getting more defensive scores would benefit me a lot.

What would you guys do in this situation?