speed of mail() vs /path/sendmail

[Anon]

I am looking for the differece in speed/memory between using mail() and /path/to/sendmail -t

Does anyone have any experice with using both, and why are you using one over the other?

I need to send out 30,000 emails on a fairly regular bases (double opt in list for those curious). The names are all in MySQL, and I have written a class to MIME encode everything the message for plain text and html text.

thanks