Honestly, winter OC is as much about the coat as the holster. My criteria for a OC coat are:
1. Provide enough warmth
2. Short enough to ride on top of the holster
3. Cinch at the waist to prevent accidental covering due to movement
4. Tight enough to the body to not interfere with the draw
I have a coat with a inner lining/outer shell that can separate. The inner lining is good for OC. It's short and has bungee cords to cinch the waist. The outer shell is way too long for OC. I have a Galco and a Serpa holster, both OWB. The Galco rides close to the body, the Serpa sticks out. (I don't own one, but I know Safariland sticks out too) The Galco doesn't provide much room to tuck the coat without interfering with the draw. The Serpa works much better in that regard.
As with any form of carry and clothing, unload the weapon and test things out. Move, walk, bend, stretch. Know how your clothing and firearm will interact together. Practice drawing and reholstering. Can I get a firing grip while holstered? Can I actuate the retention mechanism? Does it snag going in or coming out? Do I have to adjust the coat prior to reholstering?
To be perfectly frank, the easiest and safest way to OC in the winter is with a CPL. It won't matter if your coat covers any portion of the firearm.
TL;DR: It's the coat, not the holster