Lookout Trail is a reasonable 2km loop that treats you to one of the most perfect Algonquin landscape views, period.
But it's not my top recommendation. You see, it's so beautiful, that it's a victim of its own success. It can get so busy, that during the now world famous "fall colours" season, it feels a little bit like Canada's Wonderland of hiking. It's a convenient trail with a postcard perfect lookout view. Your total hiking time is about an hour (or less, if you want to rush). And it's directly along the Highway 60 corridor.
So that's why I recommend this trail in the winter time. Having Lookout Trail all to yourself in knee deep snow, on snowshoes, with nobody around? Pure heaven.
Please remember, parking along Highway 60 is illegal. If the Lookout parking lot is not plowed, you can park at the "Big Pines" parking lot. The Big Pines parking lot is an official winter-maintained parking area. You won't get towed, and if an emergency happens, your car will be an ideal place for EMS to respond to.
The extra distance between Big Pines parking lot and Lookout trail adds about 2km to your hike, making this about a 4km winter experience. Ontario Parks built a safe trail that connects the Big Pines parking area to Lookout Trail.
You move a lot slower in the snow, especially if you're doing a trail that is harder to access, like Lookout in the winter. Because you're parking at Big Pines budget enough time and energy so that you don't get caught hiking back in the dark. I would budget approximately 3 hours total snowshoeing time - to do it comfortably. Athletic and experienced snowshoers could probably do it faster, and less experienced may easily take 4 hours. Use proper judgment as you plan your trip.
Happy snowshoeing!