Here's a link to the AAHA guidlines that you can print and bring to your vet:
https://www.aaha.org/professional/resources/diabetes_management.aspx. Point out to your vet where it says (under insulin therapy in the cat) "The insulin preparations with the appropriate duration of action in most diabetic cats are glargine (U-100) [Lantus] or the veterinary-approved human protamine zinc insulin". When I get back to my computer, I also have another, more recent article you can also print that goes into more detail about dosing and remission rates that I'll post here for you. Most of the time, the wrong treatment gets recommended not because the vet is bad--they just don't know the correct treatment guidelines for cats and need the right information. If your vet still insists on a different treatment path after reading the articles, then it's time to find a new vet.
Even vets that get some things right can be off about other things. When Bandit was diagnosed back in 2009, all of these guidelines were still very new, but his vet was very forceful told me I had to home test (and that human meters were fine), handed me a list of low carb, commercial canned foods in different price ranges, and gave me a script for Lantus. All good things, except her dosing recommendations were WAY off because she had two diabetic
dogs, and adjusted Bandit's dose like a dog, in whole unit raises and only having me shoot once a day. I found this site and read the current research and dosing protocols, and when I confronted her with the correct published dosing protocol, she insisted that her protocol was better because she had great success with it in all her dogs. *facepalm* Because she wouldn't work with me, I switched to a vet that knew much less than her about the correct treatment, but was willing to read and follow the material I brought her, and we had a great relationship for many years until I had to switch vets again last year when Bandit started having health issues her practice didn't have the ability to diagnose (immune-mediated myelofibrosis, unrelated to his diabetes), and he now has to see an internal medicine specialist at Cornell. Fortunately, Bandit's new vet is very knowledgeable about feline diabetes and advocates the exact same treatment we do here, so no arguments were needed with him! However, I still bring my younger cat to the other vet--we established a very good relationship over the years and we always have a good rapport, even if we disagree on something.