It depends on your loss and your environments.
If you’re not in environments that would utilize echo block (or not that often to justify the cost), then there’s not much more difference between them.
Convenience is one of them - 90 have ‘speech in loud noise’ available as automatic program. Echo block also (that one isn’t available in lower tier at all).
But from how well you will hear with each of them in regular environment - if they’re set up properly and the same, you’ll hear the same.
In quiet, even 30 will give you the same results as 90.
If you struggle with speech comprehension, the cause might not be your aid, but your loss.
Eg if your word recognition score is lower than 90, like 70, no aids in the world can push you back into 90s.
Or if you struggle with noisy environments eg you need signal-to-noise ratio of more than 5.
Both of those are ‘features’ of our brain, and cannot be helped with hearing aids alone, if at all.
So, if you can share with us your word recognition score and your SNR score (quicksin or something similar), then we can tell you if there’s a chance you could get something more out of them or not.
But easiest and fastest way is to try them both. Although, in all regular environments they should work the same, especially quieter ones.
However, it’s of the utmost importance that you have a good fitter, and not the seller.
Seller will intentionally set up more expensive aids better. So such comparison can’t be a fair one.
In short, find a fitter who can give you those numbers and whom you have to convince why you’re better off with more expensive aid.
Then you’ll know you’re in the good hands and that trial is fair one.