What are your position coordinates?
THose two bikes are quite different in geometric philosophy

On an essentially "money no object" build like these two options, I can't imagine not running Dura Ace on the P5x. Other than that, as Cyclenutz said it surely comes down to which fits you better (plus which you think looks better).

Why?

Looking at the two options and comparing to what he's selling, the OP isn't likely to be getting any significant speed gains out of the switch. So it comes down to essentially the feel-good factor of having the very best available. For me, buying a second tier groupset and putting it on one of the most expensive framesets available doesn't fit the bill.

I'm sure both are amazing, so go with what makes you more excited. Sounds like you are a strong rider, so fitting on either should be easy. Though, I think the P5X will have more range for front end changes. If it's 650 cheaper, use the extra money and get a Power Meter if you don't have one already. Which one is easier to service, travel, and warranty? Guessing p5x may have more local bike shops that could handle things if something goes wrong.

Can't go wrong with either!

Not having experience with either of these bikes, just seeing what people have posted about them, I see no reason to go with the P5x over the Canyon. Sure, it tested as the fastest bike in the tunnel (Kiley) but I would be willing to bet a couple dollars that the Canyon could give it a real run for its money. How much storage do you need? I'd say all you need is a compartment for your flat kit, which the Canyon covers. You shouldn't need all of those ridiculous other compartments on the P5x for racing; maybe training though.

If we're being real here, the difference in "speed" between the 858 NSW and the HED Jet 6/9 will likely make up the difference in speed between the frames, if there is any.

If you are going to be traveling every other weekend (which it doesn't sound like) then the P5x might make a bit more sense, just use that extra $650 on the bike bag/box specific to that bike. Otherwise though, packing up the Canyon twice a year will be fine I'd say. Hell, just use TBT to get it to Kona.

Buy the Canyon.

From a performance standpoint, the two are likely to be very similar. The Canyon is a classic look and obvious Kona dominator. The Cervelo is an attention getter. My personal preference is the Cervelo, but everyone has their own desires. To me, Canyon = Blend; Cervelo = Ignite.

Here in Europe Canoyon have a less than stellar track record when it comes to warranty claims. I personally know several riders who’s attempted claims made them rue the day they chose Canyon. Awesome bikes, but just hope you don’t have any issues.

Personally, for that amount of cash I’d go for the Cervelo because their claims reputation is fantastic. It saying they don’t have issues, but they sort it out when they do. Wouldn’t dream of handing over big money to Canyon.

Yes that would seem strange but What about the wheelers as well ?

Nothing against Hed but are they even close to Zipp NSW wheels ?

Also have to consider LBS support which Canyon of course won't have

In what sense?
In performance I have no doubt the difference is negligible and I'm not sure the Zipp wins.

Prestige/Snobbery wise, Zipp probably wins. That's as good a reason as any to pick HED ;)

If you really want people to know how much you spent on your bike and it's not about performance, you could always get the HEDs and stick a few large denomination bank notes under some laquer on the rims in place of decals!

 
Rim brake tracks on NSW's are awesome. Hub's not so much, as they require frequent service.

I hope you weren't attached to that money...
From Tour Mag testing:


The gap is much narrower if the Canyon is in TT configuration instead of Tri.
The P5X has tilt on the bars too, which can be a significant factor in getting into best position.

I like the Cervelo P5x. However, comp is not as good as the Canyon.

And HED Jet Black wheels are renowned for their fantastic turbine brake tracks. Also, unlike Zipp, they have no hub problems I'm aware of.