killmonger could have dispatched of T'challa permanently during their ritual combat had there not been intervention; and what's more he could have done it with relative ease. Whilst Nolan's batman could almost certainly get the better of a de-powered T'challa, it is unlikely that it would be in the same convincing fashion. Killmonger also displayed combat capabilities which leave me inclined to think he could take on Bane with much less trouble than batman did. Based on (albeit somewhat limited) feats on MCU killmonger's side, i'd put my money on Erik.
P.s. Not really sure if the above counts as a spoiler, but rather safe than sorry I guess.
MCU wank really is ridiculous if people believe some random FBI agent with little to no feats can kill a guy who can dodge bullets, kick through a brick wall and beat 20 armed thugs at the same time without killing a single one of them or using any weapons.