As I have both, it's still a tossup.
The International can be built to be versatile, but it's a tradeoff. Longer tradition, better clearance, heavier, and limited on the # of speeds, etc. Will be sort of heavy no matter what. If you ride with people and need to keep up to 16mph plus and it's not flat, you will get some great legs eventually. I think it's by far the prettier of the two. Such an elegant frame. Easy for touring, not for pace lines.
The Miami Vice is as iconic, but for different reasons. It was Joe Sixpack's tri-bike and flipped off the world with it's colors. Easy to make fast, no eyelets, limited clearance to 700x25 and "smallish" 700x28's. It will do 100 miles solo or in a pace line and not beat you up or make you tired. Chicks dig it.
I voted Ironman, but I'm still building my International and its a bit more fun to deal with the funky old stuff. For my type of riding, were I to have an Ironman already, I'd take the International over another Ironman, but if I could only have one, I'm not sure I can ride SW WI, Wildwood MO, or Thunder Ridge on the International..