There are some basic considerations to protecting a ukulele. Value of the uke and the environment.
If you spend $50 on a ukulele you may not want to spend $100 on a case, unless the ukulele has special significance that there is a need to make sure it is protected. And as the value and cost goes up and the inability to replace it goes up, there is a greater need for a better case.
If you are in an environment where the uke is never going to be subjected to harsh treatment, nothing is gong to fall on the instrument and the case is merely to protect it from dust, then less can be spent on a case. I know some people leave fairly expensive ukuleles out on display.
However, if you plan on taking the ukulele out into the world so to speak, you have to consider how harsh the environment will be. If I am going to carry a ukulele on an airplane it goes in a hard case. If I am going to drive someplace I have used both a hard case and gig bag depending on which instrument I am taking. There is also a security/locking aspect when traveling that I won't go into.
For my experience, most of the damage that can happen doesn't occur when transporting/storing a uke in a case, but when using it, setting it down, playing and turning into something, etc.
John