DeletedUser38766
It's not +6/+6 attack bonus, it's +6/+0 while attacking (your offensive battles) and +0/+6 while defending (city defense only). This is the same form all non-GB military boost takes.
I'd personally take the attack boost if your intention is to be into combat heavily and to advance at a reasonable pace. If you plan to play the GB game primarily and drag your heels then the FP one will give you a bit more of a head-start on your GBs but in the long run one event building won't matter much.
Aah I didn't know it worked like that for non-GB military boost. I am leaning towards earth pagoda just because if I can level up my GBs faster, then I can get that attack boost as well. But I guess, for those who already have a high level arc, fire pagoda might be the way to go