The main difference is the Kodiak is high stretch. The zipper used in the Kodiak is a dry suit zipper. The Kodiak also uses the ankle, wrist , and neck dry suit seals. A lot of people who bought the suit with a hood find the hood to be way too big. I personally own the Kodiak and I was comfortable into water temps in the high 40's. I have heard that the high stretch suits are not as good at maintaining warmth at depth, but I do not know how much of a difference there is between the two suits as far as that goes. However. Between the two dives I did with it, 80 feet I was colder than at 60 feet in equal temperature. The trade off however is that the Extreme may take a long time to get into, as standard neoprene at that thickness will be difficult to get into. I can get into my Kodiak quicker than my 4/3 suit. The biggest complaint I have about the Kodiak is the zipper. SInce it goes across the front horizontally, I find it near impossible to close completely by myself. If it was diagonal like the dry suits from Pinnacle it would work so much better. I do find it to be very comfortable and it makes the quarry I use much more comfortable. I would like to find better gloves though. Pinnacle has 7mm boots with and with out merino liner and the same with the hoods. I actually ordered the dry suit hood. My 5mm gloves were to thin. I'd like some dry gloves to use with this suit.