Haven't paddled either... I agree that the Algonquin is more likely to be the most comfortable solo choice. I've spent many hours paddling symmetrical canoes reversed and having the ability to solo a tandem easily has been great over the years. IIRC the Algonquin's seats are set very low so if you're a kneeler when soloing they might need to be raised so you can get your feet underneath.
The larger Quetico seems to be the more serious tripping canoe, with the greater volume providing more capacity on long trips, and in cold weather, when more gear is needed. It might be made to solo more easily with the addition of a kneeling thwart but the larger size might make it more prone to being blown around by winds.
The thing that kills the Quetico for me is the partially flat-bottomed hull which I can't see being a good design feature... OTOH it might actually work out well if the hull is heavily loaded on a long trip... lots of good reviews for this one as a tripping canoe. The Algonquin OTOH was designed by David Yost, and his designs include good hull performance, in this case for novice paddlers, stability being a main requirement.
