What matters more: AP or well-roundedness?

When it comes to taking AP classes there is a diminishing returns effect. No APs vs taking 2 APs is a huge difference. Taking 2 APs vs taking 4 APs is still a big difference but less so. Taking 10 APs vs taking 12 APs is basically no difference to admissions. I’m taking about total APs here through all 4 years of HS.

Take what interests you the most, not what might appear better. If you want to do STEM, AP Stat will show more focus. It’s also a very useful class for social sciences as well.