So it looks like NGK BR6ES are more readily available locally, and less expensive than standard B6ES. Plus, they will suppress electrical noise from the engine. Is there any reason not to use them?

Nope, go for it.

I believe the stock wires have resistors as well. Not sure what effect having both would do.

--DD

I had a '71 0pel gt that I rebuild when I was 19 everything was great, new dizzy, new wires, dizzy guts...it would not start for a week before I bought new non-resist plugs. Fired right up after that.
VERY limited experience but I offer it.

Depends on your ignition system, with the stock system you will get a much stronger spark with the non-resistor plugs. I have an MGB GT as well and it runs terrible with resistor plugs and the old Lucas system. If you have installed a modern ignition system you can use the resistor plugs.

Thanks for the feedback so far. Does a Pertronix with matching coil count as a modern ignition? I'm guessing the hotter spark is the key here?

I only use the bosch super plugs (copper core) for stock, no exceptions.
NGK for performance ignitions, CDI, MSD, etc., but in these cases I'd be using wires like magnacore, etc.

Pertronix is just like the points, it's not a CDI of any sort.

Finding Bosch plugs is a bit like chasing down the rabbit hole because of Bosch constantly changing names and part numbers. As near as I can tell, the Bosch Super Plug cross references to the WRCC+ plug which is a resistor type plug. Do you know if that's true? Do you happen to have a current part number for the plugs you use?