For long guns, Pelican makes 4 levels of cases...Protector, Storm, Air and Vault. And for the most part they are in that order.
Protector offers the most protection and is the strongest but at the cost of being the most expensive and heavy. Call it a "no compromise" hard case.
The Storm saves a bit on weight and cost, but with a little less protection. How much protection I'm sure can be measured in a lab, but will certainly be tested by baggage handlers.
The Air case is one more step towards a lighter case with slightly less protection. I will also say they don't offer a true long gun case in this style. There are a few members here (
@Ed Lally) who have takedown rifles in a Pelican Air case with custom made foam. The advantage being that it doesn't LOOK like a rifle case. Lastly, there is no rating on Air case being weather resistant or watertight.
The Vault series...again another step in making a hard case more affordable, but now this case is "weather resistant". The Protector and Storm are both listed as "watertight".
Decisions, decisions, decisions. We all have to make them if we choose to travel with firearms. I will only say that I've never heard anyone complain about how much their rifle case cost when their firearms arrived in good condition. My wife and I choose to travel (relatively) light with each of us having a single Pelican Protector 1700 case, each with just one firearm.
FYI - You are just scratching the surface with this thread. There are about a million other choices out there in the polymer case world, not to mention all the aluminum options. Do a search and take a look at what other members have posted about some of these cases and you will get a feel for how well they perform.