Lots of places in both those areas to stay and to fish. It depends on what species you're after, and that will dictate which lake you'll want to hit. Orillia borders both Lake Couchiching (Perch, pike, whities, some walleye) and Simcoe (Whities, Lakers, Perch, etc.) Once you head up into Huntsville, you're more into Laker and Walleye territory.
My bet is on Huntsville for a nicer area to stay, access to lakes is a little more limited. With Simcoe, you can pretty much drive to the end of any of the lines between Barrie and Orillia to find access to a medium sized village of ice huts.
Hope that helps,
GR