Darius imho. His wins over Quicksilver Hill and Griffin suggest that there wasn't really any need for his promoters to keep him protected in Germany, except to spare him a beating at Jones' hands. He had an excellent jab, he was well conditioned, he mixed up his punches very well, and he had guts. I think his assertiveness would guide him to a victory over Collins. Collins was very good, even though his signature wins came against older versions of Benn and Eubank.
I like Collins and Roach to come up with a plan to negate Dariusz's jab, probably moving in and out of range, giving him angles and pouncing. Dariusz had a great left jab but I don't think he really had a lot else - he completely failed to open up Rocchigiani's defense in any way. He had a heavy right hand, he applied steady, methodical pressure; decent fundamentals, but he wasn't all that. Steve outworks him, and in a way, outboxes him while being awkward.