Ok...

This is my question: Do we have a solid answer on what exactly is the most challenging difficulty setting to use in custom battles and in a campaign?

I'm hearing that M/M is the avg challenge (of course) but what I don't exactly understand, due to the moral/charge bonuses is if I'd find a better campaign challenge with a VH campaign/ hard battles, VH campaign/VH battles etc...

how about in custom battle set up?

I'm about to start a campaign with a barbarian faction and would love to know the facts ahead of time...

Thank you in advance