Having personally observed this force at play in Open Source for the last year now, I see the key benefits of:
- Holding people accountable - if all the facts are exposed, there's little to no wiggle room for any misunderstandings: intentional or not. Pass thru the data and minimize the "spin". Allow people to make decisions based on real data.
- Fostering discussion - as a corollary to the above: examining data allows for questions, interactions, and analysis from several angles. Any results are more keenly understood, with less assumptions.
Specific to software, it's what RFPs and POCs have attempted to sift out for years. Nothing facilitates it better than Open Source. You have access to everything in the company, from the source code on up. Download the product, see it in action, read thru the docs -- and -- directly compare what it does to your key business requirements.