I would like the torque converter to stay locked up while I am using the exhaust brake, but still drop it out of overdrive if I choose to.
If I use the brake light switch, and I want to use the brakes and the exhaust brake simultaneously, that would unlock the converter and reduce the effectiveness of the exhaust brake. So that pressure switch would probably be the way to go. Once I get the truck down to 40 miles an hour or so, the exhaust brake probably isn't needed.
This truck is always very heavily loaded, with a big camper in the bed and/or my race trailer behind. So I actually prefer a mostly manual control so I can use my senses and my brain too make decisions rather than rely on an inflexible automatic device.