Tried to post this poppet vs CSRV picture on the other site and it failed. Might fail here too. Poppet on left is a bigger assembly. CSRV is lower, less complex, easier to manufacture and less expensive overall.
HEY IT WORKS!!! on this site.
It took a while but finally made it on the other site.
http://i64.tinypic.com/33ym2hf.jpg