I do not have experience with both, only Costco. I have the KS8 aids which are made by Rexton/Signia. A couple of years ago Consumer Reports used a survey of about 17,000 members to rate hearing aid providers and brands of hearing aids. Costco rated #1 as a provider, and TruHearing was not on the list. The Costco Kirkland Signature hearing aids rated #1 as well. At the time the survey was done, they were being made by Rexton/Signia, but users may have had older ones. In brands Signia was #2. And Phonak was down just a touch. The KS7 and KS8 aids were both made by Rexton/Signia. The current KS9 aids are made by Phonak.
The current KS9 aids are priced at $1500 a pair in the US. The Rexton Adore Li aids I believe are priced at about $1800 a pair. They are very similar to the KS8 aids but are rechargeable. These are both premium level aids.
I see from this link67 that the TruHearing “premium” aids start at $1,495, which if it is a per each price, is quite expensive.
I think it would be really hard to beat Costco for quality and price. Their initial fitting and unlimited follow ups are free. They can be returned for up to 6 months for a refund. Costco also do Real Ear Measurement for fitting the aids properly. Many other providers skip this step.