Although I have used both CPython and Stackless.py, the specific differences are fading from my memory. While working on a Go style select() for stackless.py I recall there were minor differences in how the runnable list is represented and accessed. However this is really an implementation detail. For the most part, they are pretty much the same.

The biggest difference I remember in the current stackless.py implementation, the move to "continuelets" resulted in the inability to pickle "complex" stackless tasklets. So it becomes more difficult to stop a tasklet in one thread and restart it in another. Maybe the ability to control the recursion depth (including getting rid of it) may also be gone in stackless.py.