Hello TomT,
I tried the non Merino Elastiprene 3mm on and other than the collar lump in the back the suit was great. I own and dive a 7mm Merino and it is everything they say it is. I dive in a quarry in Ohio where water temperatures are commonly in the upper 40s in the summer time the 7mm is right at home there! If planning to dive colder water or a lot of repetitive dives the Merino adds some warmth and comfort. If you dive a local area or planning to get some environmental information water temps., etc and use them as criteria for exposure protection. Pinnacle has suits for all diving conditions and they are built well. I am currently checking out the new Kodiak 8/6 with Merino, it is the most flexible, comfortable, and warmest "thickest" suit I have seen yet! Preparing for wreck dives in Lake Huron my wife needs that suit. Good luck and good shopping! CamG Keep diving....keep training....keep learning!