I agree with the recent responses to your question. Looking at a PP as an investment is not a good idea... I feel that there is something lost when you stop looking at the beauty on your wrist as an amazing piece of craftmanship and start looking at its resale value. I feel that buying a PP is like buying a diamond. There is a cut, colour, clarity and carat for everyone... Plus when you hear the line, for diamonds or anything else that one collects, "you can always sell it and get another" the reality is, at least for me, you will never sell it. You will most likely just add to your collection.
So my advice, find the best PP for you. If you need to take a bit more time to get that "perfect" PP then wait. I was suprised by my wife with a 5127G and love it. It is classic looking, and as many have said in this forum, you can wear it with anyting and everyting.
Happy PP hunting!