Asterisk Vs. freeSwitch

1. Running Asterisk in production with standard hardware, you cannot reliably handle over 250 concurrent calls. But with the same hardware, you can handle around 1,000 concurrent calls using FreeSWITCH without any issues.
2.When configuring FreeSWITCH is the decision to do all configuration in XML files but in Asterisk you have to do that all in configuration files.
3.In freeSwitch you can use regular expressions in the dialplan. FreeSWITCH makes good use of SQL for storing things like session data and registration data. This can be migrated off-box via UnixODBC so operating a cluster of FreeSWITCH instances on one central set of data becomes and exciting prospect. This also leaves the door wide open for writing interesting web front-ends and exposing call state to various widgets.
4. You can jump out of the confines of the traditional dialplan and ake over call control using a variety of languages.
5. FreeSWITCH remembers what is up with each channel at any given time. Because FreeSWITCH uses one thread per channel to maintain channel state, the complexities of locking and unlocking a linked-list of open channels in the Asterisk model are avoided. This more segmented design leads to fewer deadlocks and virtually eliminates channel state corruption issues. It is hard to imagine that this design alone garners a 10x performance boost but it looks like that just might be the case.
6.FreeSWITCH uses the Sofia SIP stack instead of reinventing a new version of SIP. This saves a great deal of time and complexity for the FreeSWITCH developers while opening up the capabilities of the project. FreeSWITCH has been extended in this way to also communicate with H.323, IAX2 and XMPP (GoogleTalk) services among others.
7. FreeSWITCH is compelling, but compared to a very mature Asterisk, it obviously still has some distance to cover.
8. For very specific applications like conferencing and media serving, FreeSWITCH is the clear winner. If you need a business PBX with a pretty web based front-end, you still might use Asterisk because no option exists yet for FreeSWITCH, but that should change in time.