http://shearer.org/MTA_Comparison
I have used sendmail ... but whitout touching it very much. When it came to making some advanced configuration i gave up ... it has some shitty syntax of conf files.
I asked a friend and googled around ... and finaly I choosed
exim. It has pretty good documentation ...
Since 8-9 mounths i havent touched it. It runs perfect - antispam, tls ...