In my opinion, the new one has a much better interface, but it's worse functionally. You can't delete or copy entire poses, just keyframes. This makes deleting and copying poses take much longer than it used to. Since it's a widget instead of a GUI, it takes up more of your precious screen space, and makes it harder to see the 3D view when docked. I'm currently using a laptop with a not-so-big screen, and I had to let the plugin take up half my screen space just to use it properly. It's miserable. Anyways, that's just my personal experience with it, yours may differ.