I’ve tried both over the years.
I’m mostly in cities and go city to city, and have arrived at the conclusion I prefer hard side luggage for a majority of situations. I just started failing to see the point. When I was in India for a year, it made sense - for most travel from nomad hub to nomad hub, I fail to see the point anymore.
I find hard side luggage easier to pack (personal preference), far easier to dig through, better protect their contents, if your luggage is in the vestibule of the bus and encounters meddling hands, it’s not that easy to get into - and hard sides have more utility in a majority of most situations when you’re lugging them around.
Disembarking, walking to a taxi, exiting your taxi and walking into the hotel, I always find myself just wanting wheels.
I feel like I’m wearing a giant sumo fat suit when I’m wearing a backpack in most crowded situations and just find it annoying. Often, when I’m in a city like Bangkok, I’ll be on the train and see people who are going through with these giant backpacks, bashing passengers, knocking stuff over, etc., If you are carrying a separate laptop bag, it’s even clumsier. It’s more awkward trying to carry a backpack in these type of situations versus just rolling this type of luggage through. I find rolling type of luggage like this easier to get through in larger crowds.
In my experience, in South America (Ecuador, Chile, Argentina & Uruguay) - I can’t remember that many travel inflection points where a backpack would be preferable. Example, ferry from Buenos Aires to Montevideo - is a shit show disembarking, but you’re just going to be rolling through the station and going straight to a taxi and then to a hotel.
Perhaps, in somewhere like Cuenca, Ecuador - and getting off a bus and hauling around the streets or up to a hotel - a backpack might make sense, but - in all, I think I’d prefer wheels a majority of the time.
If you get a nice one like the Rimowa or a Tumi, they will have warranties and repair centers, should you bust up the wheels, locks, etc.,
And, get a nice duffle for smaller trips where you are leaving your hard side behind for awhile.