The decision in one question
Does the guitar leave your control? If it goes in a car boot, on a bus, in a friend's van or on a plane, it needs a shell around it. If it goes from a bedroom to a lesson in the next street and back, a padded bag is genuinely enough.
The full version of this argument, including what each type actually protects against, is in gig bag vs hard case.
What to look for in a gig bag
A reinforced base. Gig bags fail at the bottom edge, because that is the part that meets the pavement when you set the guitar down. Gator states extra support at the base of its 4G bags; most cheap bags do not mention the base at all.
Backpack straps, not a shoulder strap. Two straps leave both hands free and put the weight on your back rather than one shoulder. This is the difference between a bag you use and a bag you resent.
Pocket volume. A tuner, a capo, a spare set of strings, a winder and a cable is the standard load. A bag with one flat sheet-music pocket does not carry it.
Zips. The other thing that always fails. There is no published specification for zip quality anywhere in this category, so this comes down to build reputation and nothing more — which we will say plainly rather than dress up as analysis.
What to look for in a hard case
Body shape match. This is the one that catches people out. A dreadnought case does not fit a concert or parlour body, and a case that is too large lets the guitar move inside it, which is worse than no case at all for impacts.
A seal good enough for humidity control. If you plan to use a two-way humidity pack, it only works inside a case that closes properly. D'Addario states that plainly, and a loose-fitting case makes the packs pointless.
Latches you can operate one-handed. Trivial until you are holding a guitar in the other hand.
What we could not tell you
No manufacturer in this category publishes padding thickness, impact ratings, or drop-test results. We have not dropped any of these cases and we are not going to pretend otherwise. What is above is construction detail from the makers' own pages plus the failure modes that are consistent across the category. Where a figure would have helped and does not exist, we have said so.
