Interestingly today I showed a colleague the Newton PE demo, and they were reasonably impressed, though it stopped working after 10mins, and a few other niggles, but generally ok.
I see that you are still running Newton's old demos. Those were put together in a day or so right after the integration of Newton with 3DGS to show the capabilities of the engine. Newton has improved significantly since those demos were released. You should download the "Newton stress test 1" from Newton Game Dynamics
I have seen several videos showing off the features of the "big" engines, but I have not seen many playable demos. With the videos you don't see the bugs.
It is a good thing you are shopping around before spending a lot of money and resources on your project. You will need plenty of time and effort if you are planning to integrate your game with a new physics engine. Me, I take the easy route: Newton has done the work for me
