I’ll take a warm 4/3 any day over a 2mm or 3/2 that advertises to be as warm as thinner counterparts in my relatively (52) old age. I’d rather be warm and do some neck flushes to cool things down as opposed to getting chilled and paddling around the lineup trying to stay warm during lulls. All my suits are Yamo, but there’s only so much insulation a thin suit can offer despite the source material.
If I was surfing a 30 minute heat and was much younger I may feel the advantage of a thinner suit, but I want to be comfortable and be able to swing on set waves and not worry about being cold and stiff when a proper wave roles through.