I've owned National brass Tricones and single cones, and in not one instance did the single cone have more sustain. What a single cone has is a quick attack, and that what makes it so great for gutbucket style blues. the tricone has a smooth sustain with more balance. If I was looking for versatile, I would grab a tricone, if I was looking to play straight up blues it would be a single cone.
Although I prefer brass instruments I've always liked the polychrome tricones (steel body, baked wrinkle finish) as I think they straddle the line of sustain and good tone.... Here's one I just saw on reverb...
https://reverb.com/item/5665818-2006..._source=google