Cervelo Q - '05 P3 vs. '09 P1

So I have two bikes that are in my area for a similar price and I am having trouble deciding which one I should go with,

There is a 2005 aluminum P3 for $1750

Or a 2009 P1 for $1500

Both prices seem fair to me, what I want to know for the most part is whether there is really a SIGNIFICANT difference in the performance of the P3 vs. the P1. The way I see it is that there has to be a big jump in performance to justify buying a used bike for more money. (the 2009 is a new bike, just the "older" model).

Just to answer some questions I would expect to hear, the frame on the P3 is in good condition, the components are dura-ace and in good condition (i assume 7800, was that the model on 2005 bikes). They both fit almost identically (the P3 seems to be a little steeper due to the way the seatpost is vertical instead of angled). And in all honesty, I really do not care about aesthetics.

So with that, let the debate begin.

Thanks ahead of time.