The difference between the parlee and the supersix was quite noticeable. The sensations were completely different and I felt slow and sluggish compared to the cannondale. One thing I loved (and admittedly still miss a little bit) is how connected the Susi felt to the road. You knew exactly how fast you were going. It felt stiff and harsh, but handle like it was on rails.
On the parlee that first day, I was about to chalk it up to condition, then I looked at the computer. Despite having been off the bike, I was riding significantly faster than I previously would on the same route. While I chalk that speed that day up to some sort of "new bike adrenaline", what can't be overlooked is how much more comfortable I was after that ride than previously. While I loved that cannondale "sensation", it beat me the hell up.
To this day, there is a little part of me that misses that harsh ride of my Susi, but then again, there is a little masochist in me. And after a year on the Parlee, I can honestly say you couldn't pry it off of my dead cold feet. The bike has a tuned comfort, but damn... push it and it will go! It really does have the best qualities from both ends of the spectrum and when it comes to handling... I thought the susi was the best handling bike I had ever ridden... until the Parlee. This is a bike you can ride any time, any distance, as hard as you can and it will act accordingly and consistently.
The susi was a balls out fast feeling bike... stiff as hell and you knew it. the parlee is a way more "refined" ride. It really is something you need to spend some time on to appreciate it.
But that said, I can see how it isn't for everyone.
I read a very similar commentary about the Super Six Evo with "speedsaver tech". Namely that it feels sluggish but when you check the numbers it isn't.
So I guess sluggishness is a subjective attribute of a comfortable bike. Subjective judgement is just guess work with conviction.