What is worse: a husband watching porn when he's away from his wife, or a wife chatting to another man and sending him photos of herself?

I agree with you. While looking at porn is not good by any means it is impersonal. Chatting with someone online is very personal and sending actual pictures of yourself is just wrong. Especially if you are married.

They are equally bad. Pornography is addictive. Men may not think it's cheating but women disagree. 

Notice all the answerers that say porn is not cheating are men. (Except Robin maybe.)

A wife send ing pictures is just as bad.

Watching porn is not 'cheating'  .. Having inappropriate conversation or Sending inappropriate photos to another man .. IS.

Not that I am a big fan of porn .. But, watching porn is a relatively harmless passtime, that someone can indulge without actually 'cheating'  ..  Without a wife present.  I am not talking about someone who has an unnatural addiction or compulsion towards porn (or sex) for that matter...THAT is a whole other matter.

I believe that it's worse for a wife to chat to other men and send them photos of herself than it is for a man to watch porn.  I don't, however, think either option is great, and I'll explain why below. 

Porn is considered acceptable by most people in western society, and this is especially true of men.  It's seen as something that "everyone watches", and in many cases that's correct.

There are several issues with porn, but I'll focus on the relationship side.  When you're in a committed relationship, there's absolutely nothing wrong with a little self-relief.  Porn, however, allows the user to seek pleasure through the objectification of another person.

If you're committed to your husband and wife, it's not really fair to be satisfying yourself over other people, when you could be focussing that lust into a healthy sexual relationship with your partner.

The dangers of flirting with other people

There's nothing wrong with talking to members of the opposite sex when you're in a relationship.  There is a line, however, and once it become flirtatious or of a sexual nature, then that constitutes as cheating.

Sending pictures of yourself to a person who isn't your partner is most definitely cheating, and this is why it's worse than watching porn.  The viewing of porn is a one way act.  The person on screen doesn't interact with you, there's no contact, there's no chance of infidelity. 

When you're speaking to someone else in such a manner, and sending pictures, you're actively seeking sexual arousal from someone who isn't your partner.  That's simply wrong.