I hear a lot discussion about the superiority of NMO over Mag Mounts. It usually ranges from very little difference to NMO being a vastly better performer. Those using mag mounts say that if the magnet is big enough and the capacitive coupling solid that there is very little difference. Those with the NMO's say that you can't get a good ground with a mag mount.
My question is does anyone have any hard data showing how much improvement can be obtained by drilling a hole and solid mounting the antenna? Someone must have studied this at some point in time or performed some experiments.