Although it's not my favorite and it pains me to admit it, Chris has the upper hand. Ugh, how annoying!
I have no real preference beyond good storytelling but you seem to have a preference and I guess I should add the one detail that I forgot in my previous post.
I've been trying to cut down on the overly long posts but I'll indulge myself a tiny bit more for a second.
From first hand experience, cheating on your partner does something that you never fully understand until you cheat for the first time. You may know it's possible intellectually but you never fully appreciate it until it washes over you after you cum...and that's the fact that you just handed this person leverage on you. You handed them a rope that they can hang you with whenever they want. You handed them a loaded gun and are asking them to not shoot you. Which, of course, they will assure you they never plan to do lol.
However, people (women in my case as I'm a straight man) are people and they have wants, too. Things make them upset and in some cases they just want drama...so they'll decide to shoot you with that gun you handed them just to do it. It doesn't have to be a case of them wanting you to leave your GF/wife or the like, but it can be.
In this VN, Chris and Marvin have this leverage already. Chris has texts, racy photos and his story on what he and Anna have done already. He has evidence to back up a claim that he's been fooling around with Anna and he need not be totally honest. He could invent other events that never happened because enough did happen to make the husband believe anything he said.
Marvin? He has a photo of Anna in his vehicle with her shirt up. That's powerful leverage. The video of her changing is just a creep shot and not harmful leverage. The photo is.
They both have a nuke and it's really whoever wants to launch it first...if either do. So I guess I should have added that caveat in the above message.
If neither use this leverage, common sense and the laws of story writing dictate it will be Chris. If both are willing, it's Chris. Not even George RR Martin could pull a twist that would undo that, lol. If the dev tried it would suck and make no sense. Again, AWAM level dogshit writing logic.
However, Marvin does have a photo that if threatened to be used against her could change the math. Chris also has that and more of that leverage l but it wouldn't matter if he never uses it and Marvin would.