I've done both ... on the same quilt.
Normally I quilt it first, that way I don't have to worry about running into the binding with my quilting stitches. When quilting near the side - I can just run the machine off the side and I don't have to worry about burrying or tying off those particular threads.
That said, once binding was complete if I see an area that needs more quilting attention I don't hesitate to quilt some more on it.