Unless cleaned and sanitized in the proper way wooden cutting boards are more likely to harbor bacteria in the cracks and crevices than the plastic ones. In many areas the health departments do not all them in commercial kitchens. I suggest a minor expenditure and by new plastic ones.
(I expect t37chef my friend o is agree as it is a topic we both have differing views)
One thing we both would agree upon is that the board needs to be free of grooves and places which would prevent good cleaning and that good sanitation techniques are required no matter hat material. Sanding plastic will open the pores o allow fools debris to be trapped and encourage
USDA Food Code allows both wood and plastc
We certainly agree that whatever material is used must be easily cleanable.
I have found little scientific evidence though that wood is " more likely" to harbor pathogens than plastic.
In industry, the biggest issues I see with plastic boards are: That they are often allowed to remain in service too long after becoming scarred and stained. And, that they are often put away wet and stacked, rather than allowed to " air dry" vertically and not touching. My university's micro-lab has done extensive testing on this stacking vs. standing issue.
The FDA issues the Food Code and the USDA contributes. It's guidance to industry. I suspect that those health departments that have banned wood have done so for a variety of reasons: The " old" wood-top tables that were often poorly maintained and required cleaning and sanitizing " in place".
And, that plastic boards hold up better under repeated high temperature sanitizing in dishmachines than wood, and therefore are more likely to be sent to the machine by the user than wood. Health departments take a risk-based approach and typically don't trust that people will use the proper dillution rates, contact times and air drying for chemical sanitization. In either case, the industry has gone to plastic. Plastic is also less expensive.
For Home use, there was this study done by some folks at UCDavis:
UC-Davis Food Safety Laboratory: Cutting Board Research
Like you said, Either material works, as long as it's easily cleanable, and handled properly.