I guess none of these systems are perfect then! As someone that switches on the system, ( I'm not a pilot and don't taxy aircraft). I have seen at first hand, many incidents with the old mirror systems; especially with crews that are unfamiliar with this type at night. Probably 90% stop in the wrong place. At LGW with old Nose-loader type jetties; this requires a tug to be attached to move the aircraft into the correct position. ( These Air-bridges only go up and down and in and out to the aircraft, no wheels to manoeuvre).
This is not such a problem with familiar crews; however, I have had to Marshall on a few aircraft myself in wintry conditions as the mirror was totally misted/frosted over and the crews could not see when to stop!