We are technically supposed to use current versions of each character, the OP didn't specifiy but I get the felling the intent was Steve Rogers vs T'Challa. Captain Americas vs Black Panthers no gear strictly h2h:
Steve vs. T'Challa = Steve 6.5-7 / 10
Steve vs. Shuri = Steve 9-10 / 10
Bucky vs T'Challa = T'Challa 7-8 / 10
Bucky vs Shuri = Bucky 7-8 / 10