I'm looking to get new tires (for my Suburban actually, but I value your opinion in such matters). I would like to get something agressive. I've seen directional tires like the Pro Comp Xterrains or the new style Kumho Venture MT's, and I like the look. I've seen good reviews for these tires, too. What are the advantages and disadvantages to a directional tread? I'm not looking for a simple tire recommendation, here. I would really like to see a little discussion on the merits of a directional tread.