Sometimes I get asked on what is my MTA (Mail Transfer Agent) of choice. Almost always I am asking “What do you want to do with it?”. Personally, in most places I install sendmail. There are cases (cases where one would use FEATURE(nullclient) or similar) where I install nullmailer, for I find it unnecessary to run sendmail.
People sometimes ask me why do I choose sendmail and not Postfix (or Qmail in the old days) or even Exim since we are running a mostly Debian shop. Leaving the monolithic argument aside (which is kind of funny when most people that use it are using a monolithic kernel OS anyway) I am using sendmail because of its expressive power. I can find a way to express what I am thinking (filtering, routing, etc) in its modem noise of a programming language or milters like MIMEDefang (IIRC, there’s a wonderful PDF presentation by Ricudis on the Turing completeness of the sendmail.cf language but I have no link to it).
It is not that I have not used other MTAs. Hell, I was even running Postfix alpha versions right after it was renamed from VMailer. And occasionally I am running MeTA1 instances. But I always return to sendmail. If it does not suit you, it is OK. Pick the one MTA that can help you build the setup that you have in mind, be it Exim, Postfix, netqmail, commercial software like Exchange or CommuniGate, whatever. If it works for you and your team, then it is the right choice. Endless debates are for people who have too much free time.
However, if there is one recommendation that I can share, this is it: If you are serious about email (routing) invest some time reading the bat book. He who can understand a complex piece of software like sendmail, can guide himself through any email system.
(triggered by a brief conversation I had with a friend this afternoon)
Managing organized complexity 
Here: http://rainbow.cs.unipi.gr/projects/oss/wiki/EventSeven you can find the presentation. :)