Aww, but I already did math today... >:
Fiiinnnnee
Assuming fighter 1 has dueling and a d8 weapon:
1 weapon: ~21 damage, ~42 damage in an AS
2 weapons: ~22.5 damage, ~37.5 damage in an AS
And then at level 11 it becomes:
1 weapon: ~31.5 damage, ~63 damage in an AS
2 weapons: ~30 damage, ~52.5...