@laikabear is right. I am very cold tolerant, I think. Ample bioprene works to my advantage in cold water...
I am cold tolerant too. When I go to the lakes in autumn (or "fall" as you would say) I use a 5+5 two pieces Cressi wetsuit with no undergarment. I usually stay at -15 o -20 meters from the surface, not more. But this makes me think that the 250 gr Seaskin garment could be enough for me, and there is no need of buying a 400 gr or a 490 gr Subgear that some people use. Buying a 400 gr or similar could make sense for particularly long or deep lake dives in full winter, but it seems anyway that the 250 gr Seaskin could be used many times and even more often so it's a good purchase for me. Thanks to you all for your suggestions