For my doctoral dissertation I completed last year I did quantitative research on employee morale comparing Holacracy and Traditional Hierarchy employees. 

I survey 500 people from 17 different departments from both organizational structures with a 5 point Likert scale for this research and found this;

Overall Mean average score for employee morale 

Holacratic : 3.96

Traditional Hierarchy : 3.265

I did a lot more calculations using this data in my dissertation but this is the most basic showcase that Holacracy promotes a better work environment for employees. If you're curious to read all of the research let me know. 

Dr. Mark Smith