Wiggy. Crew on airport and home standbys are more restrictive QRS is the better option for long haul.
I'm on a west coast USA trip. We were crew short at the briefing, a standby was needed. Unless (if there were l/h airport standbys) an airport standby had just come on duty - they couldn't be used. Delaying the flight whilst a home standby arrives incurrs additional costs and may have a knock on effect to schedules/connections. Having a ORS in a £30 room who will join us with 45mins and not delay the flight and not have duty hours issues is the best solution.