It's very random but overall, it's pretty closely balanced. Unless we get a way to automate the tests then I can't provide anything better.
https://docs.google.com/spreadsheets/d/1x9X8dVM0Wwlu34uCgFpyjB08yBs-wFa2A8-Lc0pAIyo/edit?usp=sharing
To clarify:
The UEF and Cybran PD should behave in the same way as before
The Sera PD got a buff
The Aeon PD got a nerf
Now all of the PD's are exactly the same in terms of stats, any differences come from the fact that the engine is inconsistent when it comes to hitboxes.
Relevant Github PR:
https://github.com/FAForever/fa/pull/3415/files