Those primitive SCPB pickups can definitely use the protection. If the covers affect your playing style (i.e. attack method) in any way, shape or form (and they do w/ me), that is definitely going to impact the sound. I haven't attempted to scientifically compare for any differences in electronic response. I just tinker until I find the configuration that overall works best for me onstage. That would be: no covers on the J and just the pickup cover on the '74 P (that style is so nice and round and comfy). Bridge covers mess with my RH palm muting but I do like them for a foam mute. FWIW my SC Tele currently rules the herd - with both covers on.