to me, it depends on other watches and lifestyle..
Personally, I think the Portuguese chrono is a slightly dress chrono. If you have or might buy a sportier watch in the future, then I would think you should get the white dial Portuguese. That way, you could get a black dial Pilot's watch or a black (or blue) dial Aquatimer for the second, sportier watch.
On the other hand, if this will be your one and only great watch, I'd probably suggest the black dial. While you could "dress up or down" either dialed watch, the black may be a shade more versatile for both dressy and casual.
Personally, I like the white dialed model here best. But you can't go wrong with either and to me the question needs a broader context to be answered.
Good luck,
Michael