The plus side to cargo is that you have no PAX to worry about and so the only real delays you can have are late freight and ATC slots. None of the medical emergencies and lost PAX or late catering / cleaning. THe down side is the really unsociable hours as it is mostly night sectors.
The pay is roughly the same as PAX operators but I know my fleet doesn't benifit from the cushy night stops that med haul pax carriers get and we mainly fly V. short sectors (some as short as 8 mins).
The cargo aircraft usually are worked hard and look a bit beat up but if your company is a good one you'll still get all the toys we have come to want in life (like TCAS and GPS)
HOpe this helps
Box