Pros
1) Lighter
2) Easy to carrying around
3) Quick to set up
4) Great for sports where you have to move but still need long telephoto shots.
Cons
1) Can't stand up by themselves... Now, there are mono tri-mix that have feet
2) limited tilting (try to get good ballhead mounting)
Tripod
Pros
1) Stand by themselves - Stability
2) Eliminates Shake
3) Variety adjustment for camera position and angles
4) Rock solid for low light, long exposure, telephoto shots.
5) Great for fixed photo area, like portraits.
6) Good for remote shutters.
Cons
1) Heavy
2) Bulky
If you are considering monopod or tripod, it all depends on your needs and preferences.
I'm buying my self Manfrotto 682B Self Standing Monopod (Black)
More Info:
Manfrotto 682B Self Standing Monopod (Black)