I’ve had leather panels replaced, and you could not tell it had been done. I’m told, but I don’t know for certain, that changing the seats can be a headache, as the airbag modules etc are coded to the car. I’m also told, that seats with airbags in the side, the stitching is especially designed to split when the airbag deploys, so whilst it will probably never be an issue, it should really be done properly with the correct stitching to replicate the OEM spec.