I do 12.5 gallon batches in an Extreme 100qt cooler. The problem I have with the Extreme is that when the cooler is full the sides bow out and the lid doesn't want to seal in the middle. The thing I like about the Coleman is that it has a clasp at both ends. I think this could make a difference when tying to maintain temps. The Extreme does a good job of maintaining temps if it is pre-heated. I think you should always pre-heat a cooler MLT anyway. I'm going to change to the Coleman 150qt on my new HERMS rig to increase to 20 gallon batches. I think round coolers have an advantage in the fact that the lid can be screwed, but for me they just aren't big enough.