As jrmyl said, if you're an instructor then you do more pax flying because the guys going through OJT do most of their flying on the pax aircraft.
Of my last 60 sectors, 12 were pax. A convenient 20% I thought
I think most people prefer the actual freight flying and not having the extra hassle that the pax flying entails. However, it's the fatiguing nature of the freighter scheduling that is riling everyone at the moment and it's only getting worse.