I have read mentions of portmaster and portmanager in various books on FreeBSD, but what is the difference between them? Is there a recommended port management utility?

Thanks.

I use portmaster on most of my FreeBSD boxes. (I still use portupgrade on one box; long story.)

I haven't used portmanager in years. IIRC (don't quote me on this), it was not being actively maintained at some point and became broken. But a quick look at the freshports.org records seems to imply that the maintainer is back.

Anyway, from portmaster's own manpages:
Which is to say portmaster uses tools already included with the FreeBSD base system and the regular pacakge db. Common usage is simple and straightforward, and it's well documented and actively supported.