I have a regular SGX.....not the fleece lined xero and wear my 3/2 chest zip with a hooded top underneath all winter. Water in low to mid 40s and air in the teens and was good for a 3hr session before I bailed. The SGX is an excellent suit! The 5/4/3 hooded xero runs $469 at wetsuitwearhouse regular price.
I pulled the trigger on a new 3/2 this weekend, and I was shocked at the price of some of the Xcel drylocks. There was a 3/2 there for almost $500. Wow... $500 for a 3/2! How warm does it have to be? I'll drop that kinda cash for a winter suit, but for a 3/2?
Second on the Isurus. I have two of their suits. One is the 4/5/4 i-soldier. Lightest 5/4 I've ever worn. The best part is that they they do not absorb water so you stay light in the water. Excellent suits, PRICEY, but worth it.
I will 3rd on the Isurus suits light,warm, fit me well.
The xcel drylocks arent light and they arent very durable IMO... however they are extremely warm and flexy for a good winter suit. Ive used my two winter season and although its drying out and cracking a bit, it still is warm. I used it with 4 mil gloves and 3 mil boots all winter in rhody the past two years... hopfully giving it a crack in the PNW this winter.