who will retire first, and why?

[Bobby Fischer]

Street Cry and Smart Strike may have a lot to do with it.

Smart Strike is pretty hot right now. Smart Strike is already listed 75k could even go up a little. Not sure of the age/condition of the Stallion, but with that asset already maxed out, Curlin can retire and start his own legacy whenever they feel he is ready.
Street Sense is one of Street Cry's leading runners. Street Sense seems genuinely healthy , the Bluegrass was basically a solid work, so after 2 big races, one of which was all-out, he should be fine after a month or so off. Street Cry is a bargain at "only" 30k listed as of now and it is a good bet to increase a bit on his own before Street Sense is retired. Street Sense running a big 3yo campaign could be a major asset to his sire, and his future earnings at stud.