I'm sure you'll be happiest to see it with your own eyes, but I had both cameras in my hands for a week of testing and can confirm what others have found:
The 200A is considerably more light-sensitive (about a half-stop, or asa 500 vs 320 for the 200), and much less noisy (about 9 db!). The combination of these two results in a usable low-light performance improvement of approximately 2 stops 'equivalent'. At higher light levels (like outdoors in daytime) the difference between the two cameras is almost negligible IMO.
Focusing seems easier on the 200A's LCD too, at least with EVF detail on (which it always is on mine). I think they boosted the HF response there to achieve that.
are there any tests shot with side by side comparisons that I could see
not necessarily stills maybe some video. Maybe I missed some stills so those too.
in the end it is tough unless you do the test...I could tell pretty quickly i feel if the cameras are set the same and you throw them up next to each other....you would be able to see...."oh this image is brighter"
I guess though if you are pumping gain in...you would need to see how that translates on a bigger monitor.
There was enough of a difference that when we bought our second HVX I ignored the $400 rebate on the old one and went with the 200 A.
Still use our older 200 and love it, but I personally think it was woth the $400 extra just so I never have to answer the "Is that the newer HVX 200" with a no.