I would think the only thing that really matters is time to stow carry one. Everyone has a carry on, then late groups are asked to check it but everyone wants t

I would think the only thing that really matters is time to stow carry one. Everyone has a carry on, then late groups are asked to check it but everyone wants to see with their own eyes that there is no space or people put their roller in flat, when it clearly states to turn it on its side in newer planes with drop down overhead space.