A bit of both really. The V8s in LSs have never been tuned for performance, whereas the engine in the LC was originally designed for track use and gets close to the magically 100 bhp per litre for an NA engine - and seemingly without sacrificing reliability, although as you say 200k motorway miles sitting under 2,000 rpm isn't going to stress any modern engine.
Not that these engines are bullet proof. Exhaust manifold cracks and valley plate leaks aren't uncommon but these are more related to age and number of heat cycles rather than pure mileage, and its possible that these issues have been corrected on the latest variant of the engine that is in the LC - only time will tell.