The geometry is not necessarily different from Japanese Swords made by other schools. They were many times big beefy swords but the basic geometry was unchanged. Dotanuki swords were know for their function, and sharpness not their art form, quikly becoming favorites among the Bushi class. Where some schools focused more on aesthetics, the Dotanuki smiths focused on strength,, sharpness and durability. They were known to withstand the stresses of the battlefield and return to battle day after day. When Japanese General Kato Kiyomasa, known as the "Devil General" was sent by Hideyoshi to invade Korea, he chose Dotanuki smiths to accompany him to ensure that his troops would be provided with adequate swords for battle.
http://yakiba.com/Kat_Dotanuki2.htm