Upgrade of 12 pro max to 17

To me, it would be a huge leap up, but what I think doesn't really make it a better choice for you. You should compare the models and features here --> iPhone - Compare Models - Apple

I am running SE3 on it. You will get a cleaned up Photos app, new call screening and a big change in glassy appearance which I love, some hate, can be tamed diwn. Most Search bars move down to screen bottom . Any phone 15 or older will not get many other new features. At the very least update to 18.7 while the option lasts.