I was in same situation...
If you're pretty sure its going to be one and only one, the Rolex Pepsi GMT will be my choice...its arguably the most iconic Rolex watch (of course you'll hear the same arguments from sub, sea-dweller, daytona and even DJ owners...
)
but if its a matter of which to get first, then i agree with the earlier posts. The Pepsi is not that difficult to find. IF you can find a zero with a decent price, its a wonderful piece.
all the best, and do tell us the outcome.
oh yes, supposed to make it easier for you to choose...
some old wrist shot