Having worn out the saucony triumph iso 4 (1240 km) and 5 (1350 km), having extensively tried the endorphin speed 1 and currently using the ride 15, speed 3, and pro 2, it's time for an evaluation:
The shoes are excellent! The foot goes in and feels comfortable, the heel "locks" in the right position, and the shoe hugs the foot exactly as it should.
Breathability: impeccable, whether it's summer or winter, the foot stays dry and well-ventilated.
Feel: as I mentioned earlier, the foot locks in place and stays there, giving you the sense of security you want (which was missing in the previous 2 models) to break your personal records. Additionally, the forward propulsion technology sends you smoothly forward, reducing the effort and fatigue of the foot. I say smoothly because the pro 2 pushes you forward even forcefully, as if you robbed a casino. Furthermore, there is no annoying inward tilt like the speed 1, at least.
Lacing: they nailed it! They achieved the perfect lacing! The laces are not "slippery," they are elastic enough (so that if you tighten them too much, they have some give) and velvety/soft. This way, they do not create pressure points on the foot.
Tongue: perfect? Excellent? Just the right length, so that it doesn't come out of place but at the same time protects the foot from the laces. This way, you don't need to tuck the laces inside the shoe if you're curious like me.
Performance: it is for paces of 4:55 and below. The faster, the better, they show what they can do.
Size: the toe box is narrow, so go half to a full size larger, not your regular size. I wear a regular size 45, returned it because they don't make 45.5 (half size), and got a 46 (one size larger). It's perfect.
An explanation: because I noticed some ambiguity in the sizes of athletic shoes in various reviews, especially in racing shoes, as well as in their use, therefore the result, therefore the evaluation, I want to clarify something to maybe help people understand. Each shoe is made for a specific weight category, for a specific pace category, and for specific distances. You don't just go and buy whatever. Because the speed 3 is a great shoe, it doesn't mean it's suitable for someone who weighs 80 kg or more, even if they are all muscles. And no, it's not related to height. For example, the speed 3 is for those under 70 kg, mainly for paces below 4, but it also supports 4-5 (5 being the limit) and is suitable for medium and long distances. Obviously, I also use them for interval training. There are other shoes for a fast 5K, others for long runs, and others if you want an advantage in a race. The speed shoes do it all and are cost-effective. Nevertheless, for longer runs, I, for example, also got the ride 15, so that they accumulate mileage instead of the speed shoes and thus last longer. Saucony is not fooling you, nor are their sizes fake. For all shoes, go with your regular size. For the endorphin speed and pro, go half to one size larger.
In summary: the shoes are a combination of the performance of the speed 2 and the comfort of the triumph iso 5. If you haven't tried either of the two shoes, it's like having a Nissan Skyline (speed 2) with 850 horsepower and putting a Ferrari Enzo interior (triumph iso 5) inside.
Update 7/30/23: a 180° change of opinion... Now that I have covered 710 km with them at paces ranging from 4:15 to 3:20, my opinion is negative. From 350-400 km onwards, the energy return was not the same. To reach the same pace, I struggle as if I'm running beyond my capabilities. The slightly larger size than usual now burdens me, whether in interval training or long runs. Now my ankles hurt and I have a constant tendency to cramp in my calves, something I haven't had in 10 years, even when running with €30 cigarette paper shoes. To achieve the proper fit, I have to spend 10 minutes dealing with the laces before I start running. Because I almost simultaneously bought the speed 2, the difference between them is obvious. The speed 2 are guns! While these ones are left with the reputation. I wear the speed 2 and simply run. And I run and run. Ultimately, 3 stars, no more.