I want to start learning OpenSIPS or Kamailio. (using it together with Asterisk)
Which Asterisk user can recommend one ?
It is only as a learning process.
So I’m looking for the one that is easiest to learn. 
I’m not interested in performance.
OpenSIPs and Kamailio are basically the same thing. They are both forked from OpenSER, and they both started as OpenSIPs and Kamailio version 1.4 which were identical.
Now they are both on 1.5 and are starting to slowly drift apart in regards to the modules and features available.
I decided to go with kamailio because I received a much more open response from the lead developer when I needed some help gettting started. OpenSIPs seem to have about 2x as much traffic on the users list, but the Kamailio list seems to have less posts about crashing and core dumps…