How to develop an empirical data base on Permacultures successes

Ther are so many degrees of permaculture efforts. When people ask for empirical data how would you filter categorize relevant data? An urban effort, an effort on 5 acres or less, something large scale? How does one create a repository of empirical data?

First two things that come quickly to mind are diversity of 'products' and  maybe volume of product per sqft?    I grow WAY more "things" in my urban plot than most traditional type yard gardens.

But we need to think about things like age of the project too I think.   A year one project isn't going to look like a year 5 project for most.  

How about cataloging wildlife sightings over time speaking of diversity.   Or pollinator species observed?

I'm on year 3.5 of my urban project.  I WISH I had been keeping logs/journals of bird and insect species since the first summer.  

I wish I had started better journaling at the outset. Without a side-by-side comparison of conventional and permaculture efforts how does one support their data for a particular location?
I don't want to waste ground on conventional gardening when I have seen what I can accomplish with permaculture on my property. "Show me" has to have a comparative. With the current weather in my area whether cyclical or global warming, side-by-side trials might be the way to start.