Which Alfonse build is better?

Dont use the TA effect, is much better a stat increase, change the A slot for brazen atk/def from a 4* ares.

The rest of the build looks ok, but imo a special like ignis and sword breaker is better.

Change it up. Assuming you are using him for Arena, Def or Res refine instead of Triangle Adept is preferred. You want as many bonus unit kills as possible, and blues will be extremely difficult to KO with TA.

Brazen Def/Res or Brazen Atk/Def are better A Slot options for some insane stats when damaged.

Shield Pulse/Estucheon could be interesting. I have never tried it, but I think in general Alf needs a damage boosting special to get KOs against the weapon triangle in arena.

Are you sure you want to kill a Saber now?