Having tested all 4 wrappers now, here's my assessment (based on observations of my own game):
CW7: Still the best perf; has the least jank/jagging, and the best framerate (about 10% over CW11/12).
CW10: Definitely the worst. Framerate is more unstable, and is the lowest overall: about 15% lower than CW7, and 5% lower than CW11/12. Jank/jagging is more frequent. Given that others have experienced even more severe regressions with CW10, I wouldn't dream of releasing an app with it.
CW11: Slower than 7, but better than 10. Still halts and janks more than it should. Usable is the word. Similar perf to the current Chrome Stable for Android, with the exception of higher cpu use (all CW releases are that way, and my chrome cpu use was similar til I switched to ART runtime from DAVIK, so salt grains are implied).
CW12: I really can't discern a clear difference between CW11 and CW12. I think it halts/janks a hair less than CW11; conversely, the FPS is slightly lower (1-2fps, admittedly margin of error territory).
I also tried one other game whose capx I had available: Propaganda, by Egyptoon. This was a version I had optimized myself; it's a relatively low-impact game ala Flappy Bird. Here matters were worse: while CW7 gave excellent performance (60fps during gameplay, looked silky smooth), all subsequent versions (CW10/11/12) produced lower framerates, but worse, completely unacceptable motion quality, as if every other frame were being missed about half of the time. I think the moving background exacerbated this issue, which is likely present in my game, but harder to notice given that the background is fixed, and the actors don't move very rapidly.
All tests were run in WebGL mode; I tested canvas2d a bit, but it always seemed to have jerky display and a lower framerate, so I did not test it extensively.
Personally, I've decided to release my game with v7, and upload a CW11/12 build later on if Google starts complaining again or takes the game down. If they do...I'll blame it on Google.
I would definitely fast-track CW11/12...without it, XDK is looking a bit of a lame duck. Even with it, it seems we are getting stuck with the fallout of Wirth's Law