mitts
Yep, wearing a dry top/suit they seal very well and stay bone dry. They are a very tight fit on the wrists, not quite as snug as the latex seals on a drysuit, but not far from that. If they fit any tighter would be harder to put on, hard enough now 
These were recommended to me a couple years back on the qajaq forum (greenland techniques forum) and most of those members roll alot.
Bill H.
Toaster Mitts
I think the Toaster Mitts are the warmest you will find. They are much heavier than the Level 6 mitts so should be warmer, but at expense of âfeelâ
Again though, the poster is a canoeist. The level 6 mitts have a very grippy palm that I feel is too grippy for allowing the shaft to rotate in your hand with the J stroke. Not an issue for kayaking but is for canoes.
I tried them in the store last week and tried doing a J stroke motion with one of their paddles and found them to stick and bind. The NRS toaster mitts do not do that, and are going to be warmer.
Again too, the level 6 gloves that I tried at that store seem like they are going to be very warm. I got them big enought to wear a think polypro liner under.
For me, my system will be to use the level 6 gloves when it is not too cold, add liners when needed for added warmth, and then use the mitts when it is really cold. To me this is a good system.
Matt
Strong rubber dish gloves
With poly gloves underneath. You can vary the thickness of the poly glove to suit the temperature. Also keep an extra pair in your dry bag.
The rubber glove can easily be tucked under a drysuit wrist seal to be virtually water tight. It also can easily be turned inside out to dry overnight.
Thatâs the best solution Iâve found for winter canoeing over the past 30 years.
Note Iâm talking canoeing, as the OP specifically asked about. Canât say whether this would be the best solution for kayaking.
keeping you hands warm
Kayak Pro makes the paddling mitts I like the best. They are water proof nylon with a radiant reflective liner. The mitts Velcro on my kayak paddle loom and stay there for five months. They are warm enough when I paddle that I hold the loom with my bare hands inside the gauntlet mitts.
The warmest?
Pogies, without a doubt. But they can be a pain to use. Second best? NRS Toaster mits.
Iâve been out paddling in 24 degree weather. Luckily there was a 20 knot wind blowing that kept the lake water from freezing. But there was a layer of ice on the foredeck and on the paddle!
nrs reactorsâŚhave worked well for me
â Last Updated: Nov-27-09 5:04 PM EST â
I've had their 3mm Reactors for 5-6years now..really like em'...fwiw. Towards the latter half of June they become a little warm, but really work well in early Spring up in northern NewEngland.
Think these are like ski boots, you need to go and try on, if possible, as the different gloves will fit(ie allow x-amount of air to circulate) a little different, especially at the temps you encounter.
Put your hands in the water
I just put my hands in the water. It is warmer than the air all winter long and works fine as long as the rest of me is warm and paddling fast.
When that doesnât work I use wool fingerless gloves and keep my hands completely dry.
wet is okay with neoprene
if youâre wearing neo gloves, you want them wet as, like a wetsuit, your body heat warms the water. I find my NRS Reactors are better if totally wet than if Iâm poling and water is dribbling down the pole onto the gloves. I carry a thermos of hot water to rinse the gloves in when itâs below freezing out.
Good canoe glove, Pogies are good if youâre using cross strokes and have your hands locked in place, but I prefer the Reactors as they allow switching. Around here, the yakkers swear by the Toastermitts.
in refernce to Bowler1âs review ofâŚ
Glacier Gloves. Iâve used 'em down to 15deg paddling, and my hands were just fine, might be a metabolism difference? And quite honestly, once I began to sweat in them I was truely much warmer, and found them colder till I did sweat. Iâve on occasion even held 'em in the H2o to cool 'em off. I switched from NRSâs pre-curved lined Reactor gloves and never looked back, I found the Reactors, though much thicker, to be very cold gloves as well as an awkward, uncomfortable curve.
level 6 mitts
Even though the level 6 mitts are neoprene, you really donât want the insides wet, there is too much room inside them, not like a wetsuit that fits tight. The idea of cold weather neoprene gloves is to keep the water out and allow the use of an insulating liner to provide the warmth. Though at an air temp of around 40-50 degrees these mitts are way too warm, I only use them when itâs really cold. (assuming I can force myself out to use the boats in the first place )
Bill H.
Yeah, rightâŚ
â Last Updated: Nov-28-09 6:10 PM EST â
...I just love the feel of 35-40 degree water on my hands, not to mention the wind chill between strokes. That's just a little slice of heaven...
Doesnât work that way
â Last Updated: Nov-28-09 6:15 PM EST â
As with wetsuits, the less water you get in your gloves, the warmer your hands will be. Water in the gloves (or suit) DOES NOT contribute to keeping you warm, it draws heat from your body and makes you colder. Neoprene will help to keep your hands warm DESPITE being wet, not BECAUSE it's wet. Dry neoprene is warmer neoprene.