I have both. but I actually bought a camera first then got a Marcum Showdown sonar.
I will say that the camera is more of tool if you don't move a lot. If you are sitting in a spot that will produce fish or a good while then it is pretty cool to have.
Not only can you watch their reaction to your baits, you can take the guess work out of a tentative bite. Simply watch them inhale and set........almost not fair when you have it set up.
Just use your sonar to line up your bait with the camera and enjoy.
FYI......I don't use as much as I used to, as I am starting to move around a lot more than I used to.