The plastic one is better, probably for all applications. It is quite durable and easy to repair if knicked or scratched (but so is wood). It is a real airfoiled shape and is faster than the wood ones. Plastic one is only slightly more expensive than a wod one. I would not show up at a regatta without a plastic one (unless I was Eduardo, perhaps, to offer a handicap!). Wood ones are slightly cheaper, need more maintenance? They look pretty though!
I agree with Tim's assessment above. The plastic board is simply better on all counts. It has a little more area than the wood board and the shape is a big improvement over the wood board which is basically a flat board with rounded edges. Most racers would agree that the plastic board is the biggest single improvement in the class and makes the class much more one-design. Before the platic board, racers tended to customize the wood board to the limits of the specs, and they differed greatly from boat to boat. The plastic boards are identical and perform well right from the start without modification or tinkering.
We don't call it the plastic fantastic for nothing. Only caveat: If you're in shallow areas be sure to pull the board up. It will chip, or if you ground heavily or hit a stump, you can take the tip (about 3") off. Sail after it, as you can glue it back on and fair it with Marine-Tex, or rebuild all with the same. But, even these repairs are easier than the never ending refinishing, filling, building, fairing, etc., of the old woodies.