Change battery or upgrade after a year?

I have a 4 year old iPhone 12. The battery health is at 79%. The phone is slower now after IOS 26. I was planning to switch to android someday. But recently, I switched my org and they provided MacBook pro M4 for work without any restrictions. So I am using mac for most of my personal stuffs as well(youtube, netflix and things like that). Even signed in with my apple account. Now I don’t want to switch to android as I have an ecosystem now. Should I change my battery now and use it till it lasts or upgrade to 17 next year?