Needing Help w/ GC Sader Build

[Bloody]

It's not just the 5 Int. It has the rare element; Holy.
With this weapon you can finish off anything that has low HP left with 1 or 2 Bashes. Since most of the things you are going to fight are either Dark or Undead. Assuming you get a total of 20~40 Str, you can do considerable damage with that.

Aside from that, it really depends on your own build. If your build can get the final MATK bonus from Int using a Haed, then you should stick with that. If Exca will unlock the next MATK bonus then that's what you should get.