@Calchas: I explained why I don't see that to be the case - although you could argue me wrong.

Assuming the contents of your bag are well packed (not sitting loose inside), the case will resist deformation and transfer the energy of impacts through the shell of the bag instead of into the bag.

Relevant: travel.stackexchange.com/questions/5588/…

@Calchas: And won't the same be true for a fabric suitcase, basically?

The only disadvantage you name is that the luggage inside can be banged with the hard case. But the contents of a case are not sitting loose and do not fly around in your case hitting it from inside. So you have zero disadvantages and several benefits using a hard suitcase.

Some years ago, I bought a 300$ hard case luggage (influenced by ads about its toughness). It broke on the first flight, and half the content was lost. Might have been bad luck, but for me 'never again'.

@Neusser: I asked about advantanges, not disadvantages...

@einpoklum If I drop a heavy weight onto your fabric case, the fabric will deform easily and transfer the impact to whatever is inside the case. If I drop a heavy weight onto a hard shell case, the shell will resist the impact by staying rigid, and will avoid transferring energy to the contents. If the weight is heavy enough that the shell breaks, a great deal of energy will be consumed in breaking the shell of the case, before it is passed onto the contents. My other point is about improved water resistance, which may be useful.

The advantages were named in the very first comment.

By the way, I think it's much of a muchness. I have seen hard cases and soft cases damaged by baggage machines. You travel enough and your suitcase will eventually be destroyed. The only time I check bags in now is when I am transporting cases of wine. My wine merchant puts the bottles in styrofoam in a recycled cardboard box and they survive just fine.

@Calchas: How likely is it for such heavy weights that can break a hard shell to be dropped onto a suitcase? (As opposed to being placed on top of a suitcase, in which you get some distribution of weight also with fabric suitcases). Also - what do you do instead of checking bags?

@einpoklum It will happen from time to time. For instance, your bag falls into the bottom of a container as the container is being loaded; the next bag behind it is a big heavy one and drops straight on top of it. If you think luggage loaders are carefully placing your bags gently on top of other bags .... I have some bad news for you. Your bags are being thrown, dropped, shoved. And a lot of it is now done by uncaring machines which can easily shred a case if something gets jammed. Usually, I bring everything I need in my carry on.

@Calchas: I guess I can't completely deny the possibility of what you describe happening. :-(

@einpoklum regarding "how likely" I can offer some anecdotal evidence from my own experience flying YYZ-JFK-KEF with a 90 litre backpack full of warm clothes, a foam pad rolled around them, and a sleeping bag on top. I also packed a stainless steel flask with brandy in the middle of things. After I unpacked it at the hotel in Reykjavik, I found the flask bent out of shape and the clothes soaked in brandy. So, don't underestimate the attitude of baggage handlers.

If you want to travel in the US with a pistol you would need a hard-sided case for the gun. Here's some more info on the matter: tsa.gov/travel/transporting-firearms-and-ammunition

Do you never a) travel on low-budget airlines or b) use low-fare sites to get cheap tickets? You will end up checking your baggage. Also since you don't have status on the airline, the airline and handlers won't care about treating your luggage well.

There are compromises anyway. I have a carbon-fiber suitcase, which is light enough, but sturdy and won't bend so easily. But if it does, it doesn't break.

Possible duplicate of Suitcases: hard or soft? Canvas, polycarbonate or something else?

@Mikey: That question has a bunch of specific parameters (e.g. the poster's scuba gear) and asks for a recommendation of what's the best fit for his/her case. Not a dupe, please remove the dupe notice.