Rivers is the boss. He'll be harder to defeat because he knows the mind of God. He wants you to fuck him not because he fancies you (such things are beneath him) but because it's your religious duty (and you'll go to hell if you don't.)
Rochester is an ageing Regency buck; young women should not be left in his vicinity unattended but at least he's got a conscience; he'll take your maidenhead then weep over it. Rivers won't weep over anything because he knows he's incapable of doing wrong.
If Rochester harks back to Byron, Rivers looks forward to David Livingstone and Gordon of Khartoum. He's just that kind of fanatic- and worse- a monster of egotism and greed who passes for a good man because he's got a Bible in his pocket. He's going to conquer the world on his way to conquering Heaven. It's no accident that he's been given the novel's last line- because- God help the world- he's its future.
(PS I'm going away for a few days- with no access to computers. I'll reply to comments- if there are any- next week.)