On this page you can find a comparison chart that shows the features of all three CIs in a handy format. The chart is 10 pages long so fairly comprehensive.
Your audiologist and surgeon will certainly have preferences that they work with most often and that familiarity will work in your favor. The surgeon may also have a recommendation if imaging shows something unusual with your cochlea, each manufacturer has different implants for dealing with irregular structure when it happens.
Having said all that, the one study on this found that all three preformed within 10% of each other after rehabilitation so don’t worry too much about which one has the best performance. And your audiogram has no bearing on it, as this will bypass all that anyways.
Each manufacturer has people to answer whatever questions you may have. Yes, each will tell you theirs’s is the best but in my experience they will honestly answer what you ask, and they can give you some feel for what the company’s customer service is like because the one downside of a CI is that unlike hearing aids you are pretty much committing to a life time relationship with the company…
So look at the options, get recommendations from your Audi and surgeon, and make a decision. You will never now if you made the perfect choice, and I saw options in all three that I wish I could have combined, but in the end you will (most likely) have such an improvement in understanding that you won’t worry about it.