You can choose anything you feel like you won't regret it later.
you'd be able to inter convert stamina and life later
But having max hearts isnt that useful, you only want to not being one-shotted, then you can recover all your health with foodI went for the hearts. Stamina is less important. I mainly used it for climbing mountains.
When you'll obtain Revali's gale it makes climbing a lot easier and saves you a lot of stamina when climbing large mountains. And the climbing armor makes it also easier especially fully upgraded
It depends on what people want. To me hearts are more useful than stamina. The fact is that you can't have both fully upgraded. It's either hearts or stamina and I've chosen hearts because I find stamina less importantBut having max hearts isnt that useful, you only want to not being one-shotted, then you can recover all your health with food