I am writing this while slacking off because I do not feel like working.
First, some premises: I am a rider below the level of an ordinary person who rides very badly, not someone in a position to talk about FTP, and I am now in my early 50s. Also, I got into cycling as rehabilitation after an accident, so let me note in advance that I started cycling in my 40s. Please therefore read this as a comparison from the perspective of someone who rides very badly. People who ride well ride well on anything, so I do not take comments from strong riders into account.
As I said above, I started as rehabilitation and I am old, and being an office worker my flexibility was very poor. On top of that my arms are shorter than average for my body proportions. With the accident included, I have limits on my lower back and hip range of motion, so there were so many size and fitting problems that even when I bought a frame that had been recommended and size-fitted, it did not suit me and I changed frames quite a few times.
If I list all the frames I have ridden: Scultura 100 - Scultura 5000 - S-Works Venge (2016) (rim brake up to here) - S-Works Tarmac SL6 - Scott Addict RC 10 - BMC Teammachine SLR01 - Giant Defy SL0 - Factor Ostro VAM 2.0 / S-Works Tarmac SL8 - Factor Monza / Pinarello Dogma F MY26. Since I do randonneuring I ended up separating my bikes by purpose, so from the Defy onward I have owned two at a time.
The reason I actually wrote this post is that, while reading comparisons of the Tarmac and the Dogma F, I saw posts saying performance is unquestionably the Tarmac, and I wondered whether that is really so, so I thought I would write something. Of course, strong riders and different preferences may lead to entirely different opinions. That said, considering frame character, the Tarmac and the Dogma F feel somewhat different in character, and I think it is more accurate to say that individual differences arise depending on absolute power and body weight.
I rode the Tarmac after the Venge, and with the SL6 I thought the ride quality was poor because it rattled so much; then I rode the SL8 and thought the ride quality was really good. That said, the SL8 accelerated very briskly and lightly with good handling, so I thought of it as the complete all-rounder (a hexagon). However, the SL8's stack did not match my fit and it held flat-road speed less well than the Ostro, so although I could have ridden it more, I sold it and bought the Monza. To use for long-distance randonneuring. I have not ridden the Monza a great deal yet, but I consider it a bike that suits my style and my long-distance setup. The Tarmac SL8 is good in every way, but when dancing out of the saddle or putting down power it felt a little flexy and the rotor would rub, so I thought an all-rounder is an all-rounder after all. Recently I went to an SL9 test-ride event and rode the SL9 too; the SL9 has more aero character, and since the stock setup uses wheels with carbon spokes, it felt more aero than all-round. I also felt the bottom bracket area (down tube) had become stiffer. Fork stiffness has increased as well. So I thought the SL9 focused on raising flat-road performance further and that its design reflects the recent trend. So the very next week I applied for a Dogma F test ride as well. The Tarmac and the Dogma F were clearly different. With the same carbon-spoke wheel setup, the Dogma felt stiffer and heavier under acceleration. That said, once speed built up it also had the Tarmac's brisk feel. I came to understand what people mean when they say the Dogma, which used to feel heavy and very stiff, has become brisk since MY25. Flat-road speed holding was clearly better on the Dogma F than the SL8, and marginally better than the SL9.
The brisk feel on climbs looks better on the Tarmac, but I felt there is no great difference. The reason I bought the Dogma F is that if I were to have only one bike I would probably have bought the Tarmac SL9, but since I have the Monza, which is an all-rounder (as Factor claims), I bought the Dogma F. I did not get the impression that there is a big performance difference. Because I moved only the frame from the Tarmac SL8 to the Dogma F, the frame is precisely the only thing that differs.
I am a novice cyclist with an FTP in the low 3s. However, since I ride mainly long distances, I have explained the differences focusing on how frame performance and character grow as damage accumulates over long distances. In randonneuring brevets I have ridden from 200 up to 1200. In my experience, on rides of around 100km the differences in frame character may not be felt well. That will be even more true for strong riders. Considering that the difference is felt most when you reach your limits, how about discussing frame character and performance on the basis of differences felt on rides of 100 or more, say 200? Over short distances a flagship and an entry bike are all much of a muchness.
This is not a post to stir up strife: frame character definitely differs, but performance differences may or may not exist depending on the rider's tendencies. So asking which frame is better is a foolish question. Let us change it into a question of which frame you would recommend considering my tendencies and riding characteristics... that is why I wrote this. It is not written from the standpoint of a strong rider, so please bear with me.
The photos are bike proof shots.. recent ones (the SL9 is a test ride).
