You might want to check out:
- Comparing gevent to eventlet
- Reports from users who moved from twisted or eventlet to gevent
Eventlet and gevent are not really comparable to Stackless, because Stackless ships with a standard library that is not aware of tasklets. There are implementations of socket for Stackless but there isn’t anything as comprehensive as gevent.monkey. CCP does not use bare bones Stackless, it has something called Stackless I/O which AFAIK is windows-only and was never open sourced (?).
Both eventlet and gevent could be made to run on Stackless rather than on greenlet. At some point we even tried to do this as a GSoC project but did not find a student.