Greater muscle mass = greater propulsion = faster sprinting
Solinsky is without a doubt a faster starter (from blocks), faster in acceleration, and faster top end sprint speed than Rupp.
Solinsky is also taller, probably with a greater inseam.
Its not even close in a sprint, Solinsky would win, easily.
Just because he doesn't finish as fast or gets outkicked doesn't mean he's slower when both are fresh in a short sprint.
This advantage against Rupp rapidly falls off after 400m though.