[nordsieck]

IMO, backpacks are better at conforming to size limits.

They're typically advertised by volume, so 30L, 40L, etc., so you can get one the size you want. I think carry on size is typically advertised as 35-40L. They've got all the same stuff as roller luggage - straps, dividers, etc., depending on what you want. Although, IMO, the best setup is to just get a bag with the volume you want and use packing cubes.

The great advantage of backpacks is that they're soft. Every carrier has their own "box" that your item is supposed to fit into. As long as you don't have too much stuff, you can just squeeze your bag into the box. But with a hard sided roller, it either fits or it doesn't.

[ghaff]

Fully agree. Even if it's not completely soft, a 40L-ish travel backpack is just about perfect for most trips unless you just physically can't carry.

I do have a larger travel pack and sometimes favor a slightly larger wheeled pack. But even though it's a bit heavy for any really long schlepping, it's lighter than the wheeled frame and is a lot easier to deal with on trains etc.