I've been using HAs from Costco since 2010. The first house brand ones were from Siemens. The 2nd were Phonaks. The 3rd are Philips. My W has the house brand which seem to be Phonaks. The fitters I've seen have been great. One was a user of HAs since childhood. The current one is an audiologist.
Costco offers multiple brands ... right now it's house brand (Phonaks under the covers), Philips, Rexton, and one other at my local warehouse. There are only a few manufacturers used by all the brands, but different aids are likely to sound a bit different to you. I chose my Philips HAs 3 years ago because they did music better for me than the other brands did.
They are not perfect. My ability to hear frequencies, for example, hasn't deteriorated much in the last 2.75 years, but my ability to distinguish sounds (f vs s, for example) has. HA tech has improved tremendously, but they still just feed sounds to the brain. They can't fix problems the brain has in prcessing the sounds.
Adjusting the HAs and recommending the right one is key. After purchase service is key. Costco gives 6 months, IIRC, of try-out; you can get your money back if you don't like them within 6 months. Three year warranty is standard. One free, no questions asked, replacement for each ear is included in the price. Adjustments, domes, ceru-stop are all included - just stop by, and they'll help, although appointments are needed for adjustments. If UHC matches or betters Costco's after-sale service, great; if it doesn't, be aware you might need the service.
I use my IP68 (I think) HAs on the bike so I can hear traffic. They do OK with sweat. My older Phonaks and Siemens units did not, so I didn't wear those HAs while riding.