Man-to-man, Delonte is more of a threat than Bibby was. He's a better shooter under the circumstances, and he plays much better defense.
That said, Rondo is still quick enough to get past him whenever he wants, and he won't have to worry about Josh Smith swatting all of his layups back in his face. So Delonte is a tougher matchup, but I think Rondo will have an easier time with Cleveland overall.