Originally Posted by Doge

Not a trick question. Also not something there any tests on to disagree with. This is why I think the ability to guess based on understanding the principles, experience - and testing is so useful. I thought your liked guessing.

Up a hill - say 5%+ no question to go lighter.
On the flats - little question to go deeper.

But those lighter are so light and pretty aero I'm thinking they may be as good as the deeper on anything much over 2% or rolling. And they are easier to control. This is somewhat of a change. In the past low profile rims just didn't play the aero game well. Now they are playing as well.

My point is the gap is narrowing between where you would choose aero/high profile and lower profile.