To clarify what I have said, I agree that the two yeasts in question are different. Are they different enough to care about when you are brewing what you are brewing? No, I don't think so. In fact, I rarely think that is the case unless you are brewing something completely different than the yeast in question.
I guess you just have to look at what you want to accomplish as a brewer. Denny is a BJCP style nazi who wants to emulate commercial beers to the best of his ability. I am a laid back homebrewer, more in the Papazian mode, who wants to brew beer that tastes good, without caring how close I come to a style.
If you want to brew a raisony flavored Belgian, I would probably vote for "neither of the above" and go with the plummy goodness of WLP500. But, being cheap, I would probably just use the existing yeast cake and roll with the flow. Because, as long as it tastes good, I don't care about matching a commercial beer.