My dogs have a lot of winter clothes. Even though they are GSDs. Noomi was so lucy she could herritage all Nirm's clothes, so I didn't need to buy a lot of new stuff for her...
I practice a lot with them, and then they have to be in the car for some times too. The colder the temperature is, the more of their energy will go to keep the bodytemperature normal. And I want them to use the energy for the practice and competitions, not just staying warm. And I'm sure it prevent them to hurt muscles etc when they are warmer, and don't get cold very fast after they have been in activity. I warm up with the coats on, and walk them down with the coats. I uses a brand called "Back on Track", witch have a body heat reflection in the fabric. They aren't that thick, but I put on couple of layers when it's really cold (as we do on ourself, it's better with three-four layers clothing on, than just one thick jacket), and they have to be in the car for a short time. I never let them stay in the car for long time when it's cold, just to stop in to get some groceries, and back again.
I'm not sure how cold you get down to in your area, but here we drop down to between -25 and -30 C in the winter for some periods (not this winter obvious...). We don't go for long walks then, but we have to get out. I prefer coats that are water and wind resistant, but the most important is the windresistant in the winter. For really short haried dogs, I would have preferd to have a fleece jacket, and then a winterproof jacket on top on that. And it's important that the coat is long enough so it covers the kindneys too, and aren't too loose around the neck (some coats are more for the joy of humans, than function for the dogs).
But protecting the paws are really important in the cold, since they are in direct contact with the snow.
How the dogs handle the cold, is very individual too. Some dogs hate to be cold, other don't care.
