Both in their prime. Cap has any gear/weapons he used in CA:TFA or The Avengers. Bats has any gear/gadgets he used in BB, TDK or TDKR. (no vehicles) Best of three rounds:
Round 1: Daytime in Gotham City. Batman makes an exception and shows himself during the day.
Round 2: Nighttime on SHIELD hellicarrier (on autopilot).
Round 3: No shirts, no shoes (no gear) Rogers vs Wayne. Bare knuckle brawl in a boxing ring.