Mine and I am pretty sure all of them are land and groove rifled. As far as I know BHW are the only 3 groove polygonal barrels out there. Tactical Ordinance is a new company the guys at Ritch's precision started using and they are 5 groove polygonal, GLShooter has a good bit of testing posted up in the AR section on a Tactical Ordinance 6x6.8 barrel and it's looking hot.
I love my Criterion but as long as the accuracy is equal, which it is looking like I think the polygonal would be my choice. My Criterion is on a Savage target action and set up for accurate long range stuff with a 32x Nighforce and my polygonal BHW barrels are on ARs with 4x for close hunting stuff so comparing accuracy isn't possible but I sure love the polygonal, I've been thinking about a polygonal 7mm magnum for the Savage target action, I am sure that would really sing.