I found your website – wintercyclist.com – and read about Poagies from Dogwood designs. Do you think they will perform better then the IceBike mittens that Kevin from Empire Canvas Works made me?
I have heard great things about Empire Wool & Canvas and have seen some of their work and was impressed. That being said, their mitts are not something I would use for my style of riding. They are a bit heavier than the Dogwood Designs pogies (from what I recall), and the weight weenie in me weighs in heavily on a lot of gear decisions. By far the big advantage is the dexterity component involved with the pogies; many riders use no gloves at all underneath (I choose to use a full fingered riding glove, partially for the padding). This gives you full access to your controls without any sort of compromise (shifting and breaking in even the best mittens just isn't as good as in thin riding gloves). Additionally, the pogies provide some level of protection for your riding controls. Depending on your setup, it is also very easy to pull your hands out of your pogies, do whatever chore requires manual dexterity (opening your energy bar, zipping your frame bag back closed) and then shove them back in when you are done. I could go on an on about how great these are, but it really comes down to the fact that they were developed and refined in Fairbanks, Alaska. They were used and tested by riders who were out every day in temperatures down to -55F and regularly used at temps of -30F. They work well.
I can see several restrictions on a rider that would make the mittens an attractive option, the main one would be finances. It can be hard justifying spending $100+ dollars on something you will put on your bike and not be useful the rest of the time you own it. There is certainly more utility to be had with the mittens. Another difference is probably longevity. Many of us have had Dogwood Designs pogies for years, and they are still in great shape. However, they are a bit harder to clean, and should not be washed/dried because the insulation can get packed down. Joni (the Dogwood Designs lady herself) was nice enough to restuff a pair I made the mistake of washing several times. The EWCC stuff looks like it is less likely to require maintenance after a decade (maybe after two). However, both companies seem like they will be around for quite some time and both seem willing to do repairs, so that may be a wash.
I guess my final answer is that, yes, for cycling, Dogwood Designs pogies should perform better than any set of mittens (even a set of very nice, really well made mittens).