Before I moved to Florida, I lived in Los Angeles, California, for 12 years. Now, while SoCal is a dive mecca, with magical kelp forests, sea lions, and a vibrant and lively marine eco-system, its waters are dang cold. I toughed the 58-68 degree F water out for my first 3-4 years with a 7 mm, two piece wetsuit. Admittedly, I get cold easily and there were plenty of divers that seemed perfectly comfy in their 7 mm wetsuit. But about 30 minutes into every dive, I was usually shivering so much that I couldn't hold my camera steady. It sucked. I was cold, miserable and just about ready to turn my back on temperate waters. Then I had that proverbial epiphany. Since things proceed through my awareness channels fairly slowly, and when all that chilly water finally soaked into my thick skull, it dawned on me that I should try a drysuit. (In some circles, they call this a "Duh" moment for me, "epiphany" will do, thank you.)
From that point on, I literally couldn't get enough of diving southern California. You generally had to pry me from the water. If had film or air left, I stayed on the prowl. I was warm and well dry. Between dives I merely toweled off my head, then usually unzipped myself to cool off, while "neoprene-o-phytes" poured hot water from the hot tub into their wetsuits to keep warm. I don't remember how much I paid for that first drysuit, but it was worth every stinkin' penny. Since then, I've acquired a garage full of drysuits (not a good thing from my wife's point of view) and drysuit undergarments. I'm not only ready for the next ice-age, but well-prepared for colder water of any temperature. Now, over the years I've used or own DUI drysuits, Henderson, Mobby's, Poseidon, Abyss, Mares, DiveRite and BARE. Both shell and crushed neoprene drysuit styles. There are several other manufacturers, whose gear I haven't tried, with great reputations: OS Systems, O'Neill, Andy's, Pinnacle, Oceanic, Dolphin, Oceaner and Wet Seal. All the drysuits I've used have their merits, and I'd certainly recommend any of the drysuits I've used or owned, but when you look for a drysuit, do so with the following in mind because lots of little things like fit and use make a big difference from individual to individual:
1) Get a drysuit that fits. Lots of manufacturers will make one to fit you specifically. This is especially important for your shoe size, height and weight. You don't want excess material causing you discomfort.
2) Take a PADI Drysuit Specialty course. No brainer, this.
3) Get recommendations from your local PADI dive shop for the brands and type (crushed neoprene or shell) that best suits the local diving environment and the kind of diving you'll be doing. They're in the water every day. They know.
4) I personally like a diagonal front zipper so that I can don and doff the drysuit on my own. I keep my purge valves wide open (especially the shoulder valve), so they burp air as I need them to with minimal effort. And I like a full, 180 degree chest swivel valve so I can attach my LP air hose from any angle.
5) Get your boot size about one-half bigger than you normally wear to fit the thick socks you're likely to use.
6) I've tried sweatsuits, sweaters, jeans, hiking thermals and T-shirts over the years as undergarments. Take it from me: get the silly-looking polartec jumpsuit made to go with your drysuit. It's always much warmer. And secretly, what could possibly be sexier?