Who to five star?

Alfonse, triple brazen is very powerfull, he is very usefull in arena, AA and pve content.

I vote for Alphonse, but ONLY if you're desperate for Arena scoring, if not then I'll give my vote to Saias.

Alphonse. Saias is just blue Arvis but Arvis is much more useful because of Recover Ring. Alphonse is already great with double brazen. Adding the Brazen Atk/Res seal turns him into one of the best infantry walls in the game.