I also wear the Sphere 90 and I’m very happy with them, but I cannot compare with previous Phonak models as I used Resound aids before. All my previous aids had disposable batteries, I had some concerns when moving to the Sphere since it’s only available with rechargable batteries, but all my concerns have completely disappeared, as it is the case for most people using them. I recommend that you read several threads on this forum about this topic, you will learn a lot as I have 
, for example this one: https://forum.hearingtracker.com/t/people-really-should-stop-complaining-about-the-infinio-spheres-battery-life/96617 or this one: https://forum.hearingtracker.com/t/disposable-batteries/88996.
You also mention that your left ear is very bad, have you considered a cochlear implant? I have no experience at all with cochlear implants and cannot help you with that, perhaps it would be useful if you uploaded your audiogram to your profile, I’m sure many people in this forum could give you good advice.
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