As I've got a standard (but with lot's of chrome) T'bird, AND a T'bird sport, and my son has a Legend, I thought I'd offer some thoughts.
Legend. low seat, nice black engine, highest bars of the three (at least on my lad's),5 gears. Sort of cruiser style
T'bird. Nice shiny bits, slightly lower bars, 6 gears. Standard (traditional British) type bike.
Sport, Flatter bars, black engine,6 gears, bit more power, better brakes, better suspension. A well set up Sport can really mix it with the sport bikes, especially on the twisties. Well, if you're a better rider than me it can.
As an older rider I generally prefer my standard T'bird's comfortable riding position, especially on longer rides, and I even enjoy polishing the chrome! Gives me something to do on the long (UK) winter nights.
Remember however, any of these bikes is really great, and most of the differences between models are not too great. Buy which ever you fancy, you'll love it.