Check Interco's website, they have the tread depth of each tire listed. LTB's are a little limited in size options, but they have a little softer tread compound and a little larger shoulder lugs. Otherwise it's the TSL.
Consider the TSL/SX if you want one of the toughest tires available. I'm likely going with the TSL SS because it's available in 34"x9.5" and has 27/32" tread depth, almost the most of any swamper.