It depends. They are all the same hardware, but different features enabled or disabled.
The 90 has very advanced speech processing, the 30 is sold as “basic”. The 90 has 20 “handles” to shape the frequency response, the 30 has just 6.
If you look at my audiogram (click my name), you see that my hearing is “smooth/flat” in bass and also in high treble. But it has a wicked S-kink in the middle. With the 30 that I got it is not possible to get a very-good correction for my left ear. For the right ear I will want the 50 or 70 to have 12 or 16 handles for the audiologist to fit me better.
This is the kind of question your HA Provider should help you with. Mine was dubious about the 30 for me and I admit it is marginal. But having looked at the features and MY hearing preferences, I think the 90 would be “too much” for me (too much automatic processing, and I am a audio control freak).