For antivirus software updating, I would first check with your vendor (or related documentation) to see if there are any automatic update options. Some vendors will use such technology to simplify the process and ensure that critical updates (to the software, not just the signature files) are implemented as quickly as possible. If automatic updating won't work for you, you'll likely have to rely on one of two solutions -- a general systems or patch management solution that will allow for the updating of arbitrary software, or a 'home grown' solution that may consist of some scripting (login or otherwise) or other more manual options.
Regarding the best software in terms of needed maintenance, I am not certain if any relevant studies have been made of the various antivirus offerings. I would suggest checking in antivirus forums for more information on this topic.
EDITOR'S NOTE: Here are some related links to antivirus patching topics:
This was first published in September 2005