IMO, both are equally relevant to the lobe profile. Neither is more or less important, it's the combination of the two.
How do your Brand X friends refer to split duration cams?
To be honest, I don't remeber specifics. About 10 years ago I started my Stingray project and would spend hours a day on the Corvette Forums. If asked about the cam in my Chevy I would say it's a 218/230 @.050. I think duration at .050 is the best indication of the powerband and drivability.
Wouldn't two cams with equal duration and LSA share the same rpm range even if their lift was different?