Yup, the cooler wicks the moisture away so it needs to be able to breathe a little bit. I'd go with the fitted one since it does not have that shell on it. Just remember to not leave the horse unattended when wearing the cooler since they aren't supposed to be left on.
I'm in FL so our winters are not very cold by comparison, but I do like a good rain sheet for the days when it does rain and is windy in the winter since many horses down here don't grow a very thick coat at all. I have no preference on brands, just so long as it is tough and waterproof.
"They see me rollin, They hatin, Patrolling they tryin to catch me ridin dirty"