I had the same problem choosing colors as you do. I really like the yellow one for all the reasons already stated. I, however bought the blue one, and this is why:
1. I'm a designer, so color is a big deal to me. Yellow is a fad color, which is VERY poplar right now. The reason is obvious - it's beautiful. Blue is more timeless - you won't get sick of it as quickly as the yellow. Depends on how long you plan to keep the car.
2. My brother is a cop and told me that if he sees several cars speeding and has to choose the one to ticket, he'll pick the car that sticks out the most.
3. I like the fact that my car is blue by day and black by night. It's subtle and sophisticated. Very understated, yet stunning in it's own way.
4. I like changing all the tubes and hoses under the hood to match the car. The yellow ones fade easily and get really dirty. The blue ones don't show as much dirt and grime.
5. The particular blue of the P5 is really unique, with few cars like it. You could compare it to the Lexus IS and the Civic SI blues, (roughly, not exactly). Both those cars have reputations for being very sporty, and not at all boring. So, by process of association, the P5 blue can be considered just as racey as any yellow car out there!
The bottom line is that it's your decision. I don't want to sway you to get a blue one just bacause I did. It's good that you posted this so that you can make a well informed decision. Good luck! Let us know what you got when you get it! Regardless of the color, you'll love it just cause it's a P5!