If you haven't worked on the calipers yourself then I suspect the guide/slide pins are dry and just need a clean and re-grease (garages seem to rarely perform this task these days).
Which would negate your need to shell out for replacement calipers, so is definitely worth a look.
Are you able to check this for yourself?
As for the question of vented or solid disks, take a peek through your alloys and check if the brake disk is solid or has two braking faces with webs in between. Solid are typically fitted to the rear unless it's a performance car or heavy vehicle. Also online tools usually allow you to enter your VIN to help confirm the correct components, have any asked for this?