To answer your original question - you don’t.
You either stumble upon marketing stuff, or users opinions and experiences (which are unfortunately mostly based on poor fitting practices).
Good resource are published medical articles, when you want to figure out why something works or not, eg topics like ‘does bilateral fitting makes sense’ and similar. Which again aren’t connected with exact HA model but to the principles/technologies how HAs work.
Plus getting exact data about HAs mostly isn’t useful from my experience.
Most useful thing is to find awesome knowledgeable fitter. And do your due diligence in training.
What you have to do is see which features you need, which you want, who has it, and then find fitter who follows best practices and compare directly on your ears those several candidates.
That’s the best approach you can take.
Other people opinions and experiences use to figure out what are you expecting from something or to realise that you can’t expect your dreams to come true.
There are some stuff that are backed by numbers, but are not useful to compare aids between them and decide which is the best on paper. Because at the end what matters is which are the best for your ears, including physiology of it.
Tonal audiogram is useful to see which areas are your pain points.
But to see what you can expect from HA is your word recognition score (WRS) and at which db.
If your best is below 50% that’s what you can realistically expect from HAs, and not 90%.
Second number is SNR, signal to noise, sentences in noise, basically how much louder voice you want to hear must than noise arround it be in order for you to understand it. If you need more than 5db SNR, no HAs can deliver that, so, look into additional, external microphones.
For example, my case led me to mics and if I want convenience of not having additional stuff around my neck and use phonak roger mics (since so far they’re the best), and stay with android, I basically have one option - phonak marvel. Now also paradise.
So, it would be waste of time for me to focus on others, since they can’t help me in ways I’d like. So I just don’t bother looking at them
I can’t say that I find other numbers useful, and as you can see, 3 useful numerical stuff are all about your hearing and not about specs of HAs.