I would pick Peter Maher as the more proven of the two in a slug fest. Both these guys hit like trucks and have dentable chins so anything can happen.
Ill go with Williams,both bangers but Ive seen Williams a bit and he probably possessed the better boxing skills to get his wallops across.
williams has far too much handspeed, size,strength and agression for maher. williams underated jab will do lots of damage as well.