Copper is actively anti-microbial, meaning it naturally inhibits rot from forming where it is contact with the wood, or where it has leached into the wood. In contact with wood, it also will form various poisonous compounds, most notably copper sulfate which is one of the commonly used chemicals used in preserving wood today since the banning of creosote and arsenic in most applications. It has the disadvantage of attracting moisture, but this is offset by its antimicrobial nature.

I personally like to avoid methods that will require faithful follow-up maintenance because I know that this realistically won't happen most of the time, and that people don't want the added responsibility of having the crawl under the house and clean bugs out of tiny little holes.