asterisk users - Dec 2005 - Asterisk without RTP streams vs. SER in statefull mode

I am am starting up a residential VOIP company and will be using only SIP
both with my customers and my termination provider.  I am also doing peering
with other SIP networks. My goal is to be able to avoid handling the RTP
streams as much as possible as to save bandwidth.

My original Idea was to use SER to handle the Call routing and only use
Asterisk for voicemail, forwarding, etc.  However, when talking to a
termination provider, he suggested that I could get the same results using
asterisk by itself, by setting reinvite=yes.

I was wondering what the comparative performance would be. Most of the
comparisons I've seen have been comparing Asterisk in B2BUA mode ( handling
RTP streams) to SER in stateless proxy mode (just relaying SIP
transactions). So they have been comparing apples to oranges (Asterisk in
it's slowest mode, with SER in its fastest).  To get a true apples to apples
comparison, SER would need to use functions such as t_relay() and
loose_route() and probably a few more, which impede optimal performance;
Asterisk would be configured with reinvite=yes (or is it canreinvite=yes?)
so that it doesn't have the overhead of handling RTP and thus would have a
higher performance.


With all that said, what would the performance difference be?  How many
registrations/calls can I handle per machine (3.8 GHz P4 1GB RAM)?  What are
the advantages and disadvantages of each approach?