Are you talking about the " Bronto " heads ? If you are I can say without a doubt , if I needed a head for brush clearing I would definetly lean towards them . I live about 20 miles from there base in Weare NH and when I ran my logging operation , I would have them come and mow all the slash left behind , made the select cuts look gorgeous that I was doing .
They have no problem mowing a 15" diameter tree in a heart beat , along with mowing smaller underbrush , they do all the right of way mowing here in NH for the main powerlines , they're built strong , very durable and from all the ones I have seen one my jobs and elsewhere have very minimal breakdowns . The new Evo they have looks like a sweet little head to have but never seen one in action , only the older model flail type .
But if you in the market give Carter a call over there , he's the man you want to talk with . Good luck
Later Rob