The main disadvantage is generally cost and modularity, the advantage is simplicity. With an amp and passive speaker system, you can invest separately in a good amp and good speakers. You can upgrade one without the other and you have more flexibility in how you can upgrade. Also, generally, higher quality combined speakers will be more expensive than similar quality from a separate amp and speaker combo.
Generally, most active speakers are kind of so, so, but there are some good sets made. The big thing is that they are jack of all trade type solutions. They have the simplicity of combining the speaker and amp in an easy to use package, but they also don't generally have a great amp or a great cabinet. To get one that is good, you have to pay and they are still linked so that if the amp fails you need to repair the speaker instead of simply buying a new amp. Similarly, if the speaker breaks, you need to repair it rather than simply replacing the speaker.
I generally haven't seen a set of powered speakers that I would recommend for someone who understands how to properly setup an amp and speakers. I generally mostly see powered speakers being used for foolproof setups that need to be done by average users that don't have experience. Ultimately though, if you need the ultra portability and quick setup, they may be worth the premium and upkeep costs for your situation.