I tested the attack speed of weapons, single-handed attacks fastest, while
sword/board attacks at about 73.7% as fast
two-handed attacks about 62.2% as fast
dual wield attacks about 58.2% as fast
Multiply that with max level of expertise, we get
single-handed 136%
sword/board 135.6%
dual 145.5%
two-handed 101% * two-handed weapon
The final damage is quite similar for different options.
Sword/board and dual have 1 more equipment slot, so they are better than the other two.