Advantages
releasing projectiles are faster and something you can do on the fly and can mix and match it with different techniques. You can focus on another move after you sent out your projectile jutsu. Also, once you threw your projectile, it stays on that route. Like, I spit water needles to my left, it stays on my left. I guess that's it, faster, doesn't need to much focus after releasing, and stays on the way you threw it.
Disadvantages
When you throw your projectile, you can't control it since it already left your body. Like I spit water at you, and you counter with earth wall, I can't change where it's going. It stays there, making it easy to counter and or dodge.