I can't comment on the P5. But I just built up a 7.5 frame. It's the 2017 and has the UCI legal fork, but My guess is the time difference between it and the tri-fork are negligible at best. I did sell off the UCI base bar and swap it out for the tri base bar mostly because that was an easy swap (vs fork that has to match the frame w/o looking ghetto).

Build was relatively straight forward. Cabling the front end base bars was a PITA, but nothing some beers along the way weren't able to help keep things relaxed.

So far I love it. My biggest reason for upgrading was all of the integration. My old tri-bike just had one set of bosses on the down tube. So more bottles, flat kit, nutrition, etc were all strapped to the bike in some way. With the Trek, I have two bottles on the triangle, bosses on the top tube for bento, flat kit in the speed box, and can add 2 more bottles on the seat.

For me I live in TX and where I like to ride there aren't any gas stations or anywhere to refuel on the route, so I have to load up like a camel for those 5+ hour rides in the summer.

The bike feels super fast, is much stiffer than my previous bike, handles great, and I love how adjustable the front end is. I've never been more comfortable as I can make adjustments in mm, rather than fixed intervals with traditional base bar/clamp on extensions.

I have zero doubt the P5 is also a great bike. Honestly I'd get the one that fit best and you feel you're getting best bang for your buck and call it a day. There isn't a wrong choice.

How does each bike fit you?

The SC can fit a wide range of people (I ride one). The p5 can be a tad limiting on the ranges of coordinates it can fit.

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blog

I've had both. The SC is a pain to work on and hopefully you'll never need to brake. I totally gave up using the rear brake. I love the integration. The P5 (with TriRig Alpha--and was still able to use the Cervelo beard) was a total pleasure to work on have brakes that actually work well--just needed to learn how to bleed hydraulics. Comparing the two bikes I'd go with the Cervelo in a second. I did sell my P5 to get a P3 as I travel quite a bit and prefer to completely remove handlebars when traveling and that's easy to do with the P3. I just cut rear cable and completely remove cockpit for travel. Can't do that with the Maguras. I doubt I gained more than a few grams of drag with the P3.

I've worked on a number of Speed Concepts (original and current models) and the brakes are normally fine setting up. Just use decent cables (Dura Ace work well). Ok, no one finger stoppies, but good feel, control and you definitely can lock the wheels up.

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Developing aero, fit and other fun stuff at Red is Faster

Yup. Never had any issue stopping with either of my Speed Concepts. Good pads, housing, cables and proper set up go a long way

Both are great bikes. IMO the Speed Concept has the best cockpit you can buy on any bike at the moment.

So the P5 is a "total pleasure to work on", BUT you had to sell it because you "travel quite a bit and prefer to completely remove the handlebars"? Gotcha.

Now back to the real world: the SC handlebars come off for travel in 30 seconds with a handful of screws, and its brakes are among the easiest to work on. Among other things, once set up you shouldn't ever have to touch them again other than turning a screw to adjust pad width when you change wheels. And, yes, they have great stopping power. Just as importantly, the SC can be adjusted in 5 minutes to fit almost anyone, without having to screw with brake lines. As someone who tinkers with his position almost daily, I honestly think it's close to a perfect bike. The P5 is a fine bike, but easy to work on it is not.

I am riding a SC with Zipp NSW wheels. Braking is very good
I came round a blind corner to see a car parked, and pulled the brakes hard. Back wheels locked up, and I stopped in time...
Have not ridden it in the rain yet, but dry stopping power is very good indeed

Whoa, now. I'm a big fan of the SC and have a 7.5, but really, can be adjusted to fit anyone in 5 minutes? The big flaw of the SC, along with most other superbikes except apparently the P5X is difficulty of stack adjustment. To swap a stem you need to recable the front brake and to swap a mono spacer you need to recable the rear brake, and if you have mechanical shifting you also need to recable both derailleurs. None of these operations is anywhere close to a 5 minute operation even for the most accomplished wrench. Bar tilt and a modest amount of reach adjustment are relatively easy but stack is another story. I've done Chung VE field testing with my Gen 1 SC 7.2 and for the life of me I don't know how you'd field test stack adjustments in one session with the integrated bars other than what you can accomplish with the minimal 5mm spacer. For this reason I wouldn't recommend a superbike unless you really have your position very well dialed in, and by that I don't mean an hour on the trainer with some fitter. The P5 has the same problem, to change the aero spacers you need to recable.

The brakes when properly adjusted do work quite well and are a big improvement from the Gen 1 brakes, although not as easy to work on as conventional brakes. The width adjustment is a big improvement but to adjust the width in the rear you need a special extra long allen key and for other adjustments you need to take off the cover so still not as easy to work on as conventional brakes.

My current bike has Tektro brakes, or maybe "speed modulators" is a more appropriate term. Good to hear the SC stops well. I got to check out one of the Trek-Segafredo bikes and lever pull and feel was very smooth and solid. It is a little difficult to tell whether that is indicative of all SC bikes or just the benefit of having a professional mechanic.

While I am not really interested in disc brakes, I am sort of curious if the advantages of hydraulic brakes is worth the hassle.

I would disagree about the fit anyone in 5 minutes. If you're adjusting tilt or reach/width of pads and extensions then it is stupid easy.

But swapping stems or mono spacer means having to recable. With Di2 swapping monospacer is easier as you can unplug the shifters to swap out the spacer. But if mechanical then forget it.

But if you know your stack and are comfortable with it, the the front end is a dream to fine tune for the perfect position.

You can change the spacers without having to recable. I just got my new P5 frame from Cervelo (warranty upgrade from my P4) and had my LBS cut a small slot at top middle and bottom of spacer before the two spacers went on.....no need to recable when adding or taking out. There's a thread somewhere with pictures.
ps......did my first event since getting the bike at Philly yesterday....bike is substantial upgrade over P4....braking and stability. Had no problems getting my fit dialed in.