One of the main differences, other than the obvious "Pax vs Boxes," is the side of the clock that you'll be flying on. For the most part, cargo guys are vampires that patrol the night, waiting to sink their teeth into either a cup of coffee, a Cup O'Noodles, or someone on the cargo ramp with an attitude. They typically don't see much of the sun...but there are companies w/routes during the day. In cargo ops, you will learn that, even though the field is IFR and well below minimums, if the cargo handler on the ground can see across the road, then you d*mn well better make it in!
I haven't done a lot of Pax flying, at least not 121 so can't comment on airline life, but from the couple years of corporate and now with some charter and EMS stuff, I can tell you that flying Pax requires you to be much smoother at the controls. You'll learn to tailor the flight to the needs of the passengers, such as things they like to see onboard (snacks, drinks). With corporate or charter/fractionals, you'll get to know your passengers on a personal level and will probably fly with them very, very often.
The freight world is, for the most part, MUCH more scheduled, but with Pax ops their schedules change every time you fart. What was supposed to be 1 hour of ground time, may wind up as you sitting in the FBO for 8 hours.
I miss flying freight, but I also like EMS, and the bit of charter we're doing now too. If you go freight, you'll more than likely scare the crap outta yourself so many times that it's really going to make you a good pilot. They're all fun, so think about it and ask lots of questions.
