Doing the SID first will help stabilize the sandwich. It is also easier to hand stitch around the machine stitching than vice/versa :D:D:D

I've got a top that's big and at the limits for quilting on my standard machine,so have decided to keep it simple and do a mix of stitch-in-the-ditch and a bit of hand quilting. I hadn't even thought about which to do first!