Personally, I would go the freight route if I had to choose between the two. Compared to pax flying, cargo seems to provide much more stability over the long run. One scenario that needs to be addressed is this: if hiring slowed down and you were going to spend a considerable amount of time somewhere (i.e., 5+ years), would you rather it be a cargo airline or a passenger airline?

I have never flown passengers, so I can't comment on their side of the fence. However, I'll list the pros and cons of cargo for you as I see it.

Pros:
Stability is usually much better overall.
Not much time spent in airport terminals unless as a passenger.
No passenger-induced problems from the back.
Flights are catered. (most carriers)
Wide variety of routes to fly.
Business people can conference call - freight cannot.
Going to bed early in the morning instead of getting a wake-up call early in the morning.

Cons:
Some of the pairings can be long. Again, depending on the carrier.
Night flying can be more challenging physically.
For some people, long flight segments can be a challenge as opposed to multiple shorter ones.

This list is probably inconclusive, but these are a few of the pros and cons that come to mind. I have never flown ACMI freight, but hopefully this will help give you some insight.