I replaced an Odyssey Stratos Dual Mono (not the Extreme version), with a pair of the original Bel Canto 1000's. Obviously I preferred the Bel Cantos or I would not have done it (I got to audition both before deciding). This goes back a few years now...I would have been using Silverline Sonatinas or SR17's. You might cross check previous posts as I might have commented on differences then and that would be more accurate than my memory of it. I believe the principal advantages I was hearing was a purity of midrange (greater clarity), as well as better extension up top...a bit better sparkle in the highs. Down low I think they both did a fine job, and I might have given the edge to the Odyssey. The Bel Cantos rendered a blacker background so had an audibly (or not so audibly) lower noise floor. I seem to recall feeling the Odyssey had a bit of warmth in comparison, while the Bel Canto was more neutral and linear. This was all 2-channel. These were certainly both fine options and I don't think the preference would necessarily be universal. Obviously, YMMV. I've only heard the Mk. III Bel Cantos at CES and liked what I heard but could not compare to what I had. Obviously the idea is they've improved it.
Hope that helps.
Hope that helps.