The biggest advantages to learning as an adult is on average you are going to have money to pay for lessons and a decent instrument, and are probably going to be more organized in terms of practicing and all that.
The disadvantages are that it's harder to network and find others at your level to play with. And, to be clear, the way to get good at, and enjoy music, is to play with other people. Even one-on-one lessons are a form of playing with others, and many adults use lessons as a proxy for playing with others.
Playing with other people was a very easy thing for me to do when I was coming up, and I'd imagine it would be significantly harder for an adult. But, I believe it's critical to enjoyment and success in music.