as both of them cheated on each other whose actions are worse?
Mark cheated first and on a very superficial level before any cracks started to show but Joanna never found out so did it really matter?
and Joanna cheated with her heart mostly because she felt that the relationship wasn't how it should be in a situation that Mark found humiliating
So which is really worse? And what if it was the other way round??
Mark cheated first and on a very superficial level before any cracks started to show but Joanna never found out so did it really matter?
There's a hint that Joanna was aware of Mark's infidelity. Not long after Mark beds the hot blonde, he's shown with Joanna and Caroline leaving one hotel for another (over the boiled egg incident). In their new hotel, Mark feels amorous and tells Joanna he "has an appetite." To which she replies, "Wouldn't matter who I was, would it?" Mark, of course, makes a similar comment to Joanna when she returns after her tryst with David; when Joanna kisses Mark, he coldly asks her "Are you sure you remember which one I am?"
I don't see either infidelity as being worse, though Mark clearly feels he's in danger of permanently losing Joanna during the "David" period. And since he knows he was the first to be unfaithful, he may believe none of this would have happened if he'd been more attentive to Joanna and hadn't strayed. But I think the dialogue between the two (after Mark stumbles into the pool) makes it clear they BOTH feel responsible for their temporary break-up:
MARK: I've been stupid, so stupid.
JOANNA: We both...
MARK: It was always me, really. You were always the one...I'm sorry.
JOANNA: Let's forget it.
MARK: Can we forget it?
JOANNA: Can you?
MARK: I can. I'm just glad you're back; that's all I care about.
JOANNA: Well, I'm back.