Porter is iffy in the winter, because if there's a storm, their planes can get stranded. Their island airport hub in Toronto stays closed in bad weather, and it takes a long time for them to rebound. They also sometimes have to leave luggage behind to have a safe flight in terms of weight, and it can take a long time to catch up.About 10 years ago, I used Porter from Chicago to Toronto, to watch one of the ice shows in the greater Toronto region. At that time Porter was a brand new company. The flight was a decent experience and I liked their midi-sized in-flight pamphlet.
I checked the airline reviews today. It looks like their customer service lost the initial enthusiasm.
I no longer live in their area, but I still liked them on my last summer flight a couple of years ago, although I had to pay to check a bag, which surprised me, since I never did before. I guess I went a few years between Porter flights.
But honestly, even when I flew them often between Chicago and Toronto, I avoided them in the winter.