Latency in the inter-thread communication in forks is much higher than with threads, as it uses a TCP/IP socket and Storable for it.

Thread startup, especially if you have a lot of modules loaded, should be faster with forks, as there is no copying of data-structures when a thread is started with forks (it just does a fork()). However, every thread with forks, has a bit of latency at startup, because of the setting of the inter-thread communications socket.

Hope this explains it a bit.

Liz