What do you mean by gunked up? Snow packed into the cassette? If so, I haven't had any issues yet. But it's still early in the season.
I am holding my hybrid in reserve just in case. I have the Nokian W106s on the Portland, but have found the lower bars and my preference to ride the hoods affects front/rear weight distribution. I don't remember ever spinning the rear wheel last year on the hybrid. It happens on the Portland occassionally, especially when climbing. It's not a biggie, just something I've noticed.
Are you using the Portland's stock fenderettes or full coverage fenders?