If you go the wader route please be SURE to wear a wading belt and your life preserver. Waders WILL FILL WITH WATER if you ditch your yak and it will be near impossible to swim in them. The wading belt will help to minimize the amount of water that "leaks" into your waders if you go in and the life preserver will help you float.
A better plan is to use foul weather gear as an outer layer and wear layers of thermal under the foul weather gear. The high-tech materials (LIKE Under Armor) are thin and warm and wick-away moisture like a champ. If you get dunked then, the clothing will not absorb a lot of water and will not get weighted down which will meke getting back in your yak a whole lot easier.
Whatever you do, don't forget that the water is COLD and if you get dunked then you will likely get hypothermia in a matter of minutes. Use the buddy system too - if you can!
Hate to sound like a worry wart, but cold water will kill you quick!
Whichever route you go, waders or foul weather gear. DO NOT wear any cotton base layers. Even as cold as it is, you will sweat a little underneath it all and that cotton will stay damp and soaked the whole time.
A 3rd option to consider, especially if you plan on being in the Gulf this time of year. Look into getting a wetsuit as a base layer because that will keep you warm if (rather when) you get dumped in surf.
Lots of good safety concerns have been mentioned. They are not cheap, but heavy neoprene waders add a bit more safety than rubber. They'll help insulate you like a wet suit if you do get wet and will add a little floatation. Wear the wader belt. I think the ONLY reason to get stocking foot waders is if you plan to wade trout streams where there are slippery rocks requiring felt wading shoes. Otherwise, I'd recommend a good stout boot foot.
I've worn mine for days on end in flooded AR timber in temps way below freezing and stayed nice and toasty, but they are an investment.
I use breathable waders without built-in boots. I would recommend them for several reasons. First, if you buy them in a bigger size than you need, you can wear heavy socks, fleece pants, etc, underneath to keep you warm if it is cold. Next, the breathable ones allow moisture from your body heat to escape, while rubber ones trap this and get you wet and cold. When I'm kayaking, I don't usually wear boots. I do have felt-bottomed wading boots when I'm wading in rocky rivers in Washington.