Earlier quoted context omitted.
What would be worse a catastrophic collapse deep down in the sea or a sudden depressurization high above in the sky around the Armstrong limit?
Implosion at 400 atm probably takes a fraction of a second, with catastrophic decompression of 1 atm you’ll be conscious probably for about a minute.
When a deep sub implodes you're going to be hit by water moving at the speed of sound in said water (1,500m/s, considerably faster than in air.) That's far above the speed of nerve impulses, there's no way a pain signal could reach the brain before there isn't a brain left to get the signal.