The wood vs. plastic cutting board discussion is much like the cored vs. solid hull or mono-hull vs. multi...there is no definitive answer in my opinion
I prefer wood for a cutting board. I find its easier on the knife, especially my expensive Japanese carbon steel knives.
I understand that a commercial application isn't comparable to home use, and would defer to using plastic in a commercial kitchen. Primarily because wood wouldn't be cleaned properly, the plastic can be run through a commercial dishwasher at 190 degrees +. I find cleaning a wooden cutting board with soapy water & rinse followed by a vinegar bath does just fine. In addition, a wooden cutting board is easily brought back to life by running through a planner.
One suggestion, I have one board I use only
Bottom line as far as I am concerned, whatever you choose, keep it clean and replace or repair when the board is beat up
An interesting test by UC Davis on the topic: UC-Davis Food Safety Laboratory: Cutting Board Research
Another good comparison: Cutting Boards - wood or plastic?
One in favor of plastic: Cutting Boards and Food Safety - Cutting Board Tips & Advice - Wooden Cutting Boards or Plastic?
In favor of wood: About.com: http://www.rhtubs.com/wood-bacteria.htm
The Straight Dope: What's better, a wooden cutting board or a plastic one?
Cutting board - Wikipedia, the free encyclopedia