I'll be fully transparent and honest in here since Chinatown is my family now of 5 years 
1. The Tarmac SL8 is the lightest most comfortable and crosswind-stable frame I've reviewed. Climbing on it is fantastic. The magic sauce that Specialized uses is tangible and real. I've done 6-7 hour rides on it and never really felt frame fatigue afterwards. But it's not super exciting to ride everyday, in how I subjectively quantify excitement. It's not exhilarating. It's comfy but lacks character. That doesn't mean it isn't fast. It's speedy for sure.
2. The SL8/SL7 are NPC bikes around here. Sure they are great on paper, but everyone has one. I don't care if more road feedback means marginally less rolling resistance. I like my frames to actually feel stiff because in my head that means "stomp on the pedals harder" It's why I owned two Allez Sprints and the latest Giant Propel. Stiff bikes are fun bikes. Stiff bikes feel fast. Cornering on a stiff bike is so freakin fun.
3. I only invested in the SL8 for the sake of benchmarking against other frames. Specialized fan boys (admittedly probably one myself) tell me all the time the SL8 is the one to beat, so I figured I'd put my money where my mouth is. And after 1 year of use, the frameset has served it's purpose. Same with my Propel. My YouTube channel's marginal success is predicated on constantly testing out new products. Similar to the independent car tuner channels. Legacy products don't bring in views because the audience is always expecting new projects.
4. The primary reason over everything above however is two-fold: Money and Philosophy. I can no longer afford to have several $6000-$8000 bikes lying around if they aren't getting used enough. Which is funny considering I ride 10,000mi/16,000km a year. So having an SL8 collecting dust because I don't love it is a terrible terrible financial decision. And finally, I realize I just don't "need" an expensive bike for my usage. I will continue to review Western-brands as time/budget allows. Although I suspect nothing will come close to the SL8 anytime soon. The new Scott Addict looks tasty. That's the only bike I'd invest my money into at the moment. I considered the Factor Ostro for a while but....meh.
Getting back into competitively riding my bikes in circles this season has been an eye-opener to what's important to me in a bike. I 100% feel like an idiot making that comment because I am very much still an amateur with both a forgettable FTP and skill level. I am not qualified to speak on crit racing. That said, my Tavelo Arow has been fantastic for the 11 or 12 crits I've done so far. Yes I was sent the frame. But my Yishun/LC R086D which I paid for is just as capable. Pushing bikes closer to (my) theoretical limits has taught me that both the OEM and mid-level Chinese brands are more than capable of producing great frames for their intended purposes. The resell value however is absolutely atrocious. If that's important to you...
I still would like to test an X68 just so I finally close the chapter on my SL8. I just think wheels, groupset, fitness/coach, and optimal position on the bike have played more of a critical role than the importance of the frame itself.
I feel like this isn't getting enough attention.
Do you plan to make a video about the decision? It'd also be interesting to have you chat on the Nero show about your thought process. Your choice is unique, not least in that you produce YT content and need reasons to make videos, but it still sounds like you might have sold the frame anyway because you already have other bikes that, at the end of the day, you feel like riding more. Ultimately, that's a big dent into Spec's special sauce vibe armor, and i really think a Nero show discussion would be very interesting, because on one hand, they're knee deep in chinese stuff, but on the other, Chris is still 100% invested in the idea of branded frames being a league above.
Timing would also work, given Jesse is experimenting with his own long ass stem, with your input.
