It ultimately comes down to one thing.

What do you factor more? The battery life or the form factor?

If you like the compact size, go for the iPhone 13 Mini.

If you value the battery life, go for the iPhone 13 (6.1 inch).

Also all iPhones from the iPhone X and onwards support up to 18-22 watt fast charging. So you can charge your phone really quick if you’re running low on battery. Keep that in mind.