I have the previous model of the Resound and I tried the Kirkland 4. I chose the Resound but, you would have to look at current models. The Kirkland 5 is a clone of the Resound Verso, so you can look up information about it. It appears to be a step up from previous models. Some pros just like a certain thing and get used to it and never get too familiar with anything else. The Resound software is very robust, even complicated, so if they have never used it, of course, they will not like it as well as what they are familiar with.
If I had to get new ones right now I would get the Kirkland 5. I would not make a decision about hearing aids based on rechargeable batteries, or battery life, or anything of the sort. The Kirkland 4 was a Rexton Cobalt 16 and the recharge contacts were built into the cover, and the hearing aid fit down into the dryer/charger, touching the charging contacts. No other brand does that (Just the Siemens family of brands). I liked using the charger when I tried the Kirkland 4 and they never ran down during the day, but I didn’t have a phone device or streaming device and that would probably affect battery life. The rechargeable batteries last about a year and must be replaced so you don’t really save any money.