'14 cervelo P2 vs '15 Felt B14

I know this is the obvious answer but if you can test ride both.  I bought a '14 P2 with 105, 10 spd.  I had narrowed it down to a P2, B14, B12.  Going into it I was leaning toward the B14 prior to getting any of them on the road.  The P2 seemed snappier to me compared to the Felts which seemed a bit heavier.  But that's just how they seemed to me after riding them and I am sure others may correctly say the opposite.  ETA - I was lucky to have a great shop fairly close to me that took the time to set up and adjust all the bikes for me on a trainer before I took them out.

Also, if you are planning on upgrading in the future in my opinion Cervelo's have a quicker and slightly higher resale value.

Is the P2 105 set the 10 speed or 11 speed group?  I really like my shifting with the 11-spd Ultegra (6800) I have on my B12.  I have the Ultegra 6800 crank too and the front shifting is a snap, way better than my old bike with10-spd DA R/F derailleurs & FSA crank.  I'm sure the 105 11-spd is not much diff, if any, on the shifting characteristics, likely just a few grams heavier.

The P2 does have the top tube bosses for mounting bento boxes without straps.  (Come on Felt get with it!)

I've read too that the P2 is" snappier" or "livelier" in the handling, but I prefer my TT to be stable and not twitchy.  Looking over the shoulder is an example of this coming into play. I don't ride a lot of hilly technical courses but the races in central FL with the hills and some tight neighborhood turns had no issues with the handling of the B12.  This is where riding one of each before purchasing comes into play, if possible.

If you buy the Felt you'll have some $ left over for a new set of FLO 30 wheels or a majority of it for some used FLO 60/90 wheels! 

Both are setup for the AG'er, taller, but can get low if needed, but not superbike low.  This is where knowing your stack and reach numbers come into play.

Can't go wrong with either. A lot of the time when fit isn't an issue it comes down to which one looks nicer to the eye of the beholder! 

I'm not a big fan of "get the one that fits best" responses, but in this case the frames are similar enough aerodynamically that I would lean towards the one that requires the fewest adjustments.  If they both fit about as well, I'd go with the Felt for components.