That all depends on what you want to get out of your smartphone, such as how big of a screen size you prefer, how big of an upgrade you're expecting from your current device, and how much you can afford or want to spend.
For photographers and content creators, it's usually the case that the Pro Max model is the option with the best camera and features. But both the iPhone 15 Pro and Pro Max have nearly identical specifications this year when it comes to the camera array, so it might be a wise choice to opt for the Pro model over the Pro Max if you don't have the biggest budget.