they are interchangeable in the sense that they are a jig with a blade but that's basically where it ends.
spinnerbaits are much more weedless than bladed jigs and such will come through cover better, timber and pads specifically. bladed jigs to me are much closer to a squarebill, but can be run through grass better.
the situations i use them in a fairly different but as with anything there is some overlap. keep in mind this is very dependent on where the fish are and what mood they are in.
spinnerbaits:
working through timber when fish are higher in the water column.
working the edge of a pad line (makes casts more effective because it doesn't get hung up as easy).
clearer water (more about the flash than vibration).
bladed jigs:
working above cover (over top of sunken timber).
in sparse grass lines.
anywhere its too easy for a squarebill to get hung.
muddier water, when fish are higher in the water column