When duck hunting in the deep south cold is not an issue, but probably three to four days per week. When I use the term cold it is not frigid cold like the cold you can see in the Rockies, Canada, or the Prairies of the Mid-West region. Most days the high temperature is around 50-55 and lows average around 35, but we do have our days that it is highs in the 30-40's and lows in the 15-25 range. So a big thick wader is not preferred by most hunters. 3.5 ml (unit of measuring the thickness of insulation in waders) is a usually thick enough to keep you warm on the cool days and thin enough to not get so hot on the warm days. The biggest problem in making a decision in waders for deep south duck hunting is the durability of the wader itself. We hunt lots of flooded timber in the south and waders have to tackle snags under the water, walking durability (stretching the seams as you are walking a lot), and yes even muskrats and beavers. It is a long story I will tell another time.
I called upon one my team of experts at www.ducksouth.com to give me a right answer on the question. Their most recommended waders for hunting in the deep south was "Mack Big Ditch Wader's." Their opinion of the wader was that it would hold up to most anything in the flooded timber and it doesn't let you get to hot in the warmth or to cold in the cold weather and it won't bust at the seams or stitchings from walking.
I also spoke to a local outdoor store to get their opinion on what was the best. Jimmy Slater, at Slater's Outdoor Products in Indianola, Ms, said that most of his customers preferred the Hodgman and Drake brand the best. I asked if he had ever heard of the Mack's product above and he had, but it was a product not carried by his store.
I hope this helps you as a hunter in deciding what to buy in buying your next brand of waders. Remember that you need a wader that will keep you warm and cool at the same time and waders that won't tear on under water snags or bust at the seams from walking to much.