Two-headed ogres are nearly identical to basic ogres, except for the second head. This lets them shout and grimace at you more often, but more importantly allows them to dual wield their giant clubs and giant spiked clubs.
Tips & Tricks
If you can kill an ogre, you can kill a two-headed one. Just make sure not to let them wail on you for too long, as a few lucky attacks can quickly add up to trouble even on medium-level characters.