What does the ideal power-to-provision curve look like in your opinion?

Basically, I'm wondering how people feel about this. Seems to me there are a few different relevant aspects to this question, but to keep things simple for now: If a 4p cards plays for X% of its provision value, how much should a 5p card play for? How about a 6p? And so on until 14p.

For example, if a 4p card plays for 200% of its provision value (= 8), should a 14p play for the same percentage (200% –> 28 points)? Should it play for a lesser percentage (e.g. 150% –> 21)? Perhaps even only as many points on top of its provision as the 4p (i.e. 14 + 4 = 18 = 129%)?

Obviously factors such as pointslam v. engines v. control play a factor there, as do carryover points and how conditional the value may be, but for now I'd appreciate it if people kept the discussion to this more abstract level to keep things simple.

My personal feeling here isn't settled, but it goes towards the latter of those examples, as the way I see it there's an opportunity cost to playing low provision cards over high provision ones, so it doesn't matter if a 4p is technically more efficient in terms of power-to-provision when playing a 5p or anything higher beats it in absolute value.

But what does everyone else think about such things?