Just a datapoint....four of our five airplanes have landing lights, and all are locally grounded. No problems with any of them - the oldest plane is 29 years with close to 4,000 hours, my RV-8 has 15 years and 2,000.
For the record, we recommend grounding Flyleds landing lights locally.
No need for the extra voltage loss, and our lights don't generate any electrical noise.
Local ground will be fine. Just do it correctly. Here is what Aero-Electric has to say on the subject:
Ground connections on a metal airplane are relatively simple but some cautions should be observed. First, clean all of the paint, primer and corrosion from around the hole which is used to ground a connection. A round wire brush with a pilot in the center is called a "bonding brush." It is designed to be used in a drill motor for this type of cleaning.