No performance difference. Colnago introduced sloping frames in the mid 2000's, at least in their C series frames. It was the trend for all manufacturers to reduce costs by offering fewer sizes and sloping frames allowed more people to fit a given size. That's it, despite what marketing claims they liked to make at the time. They would probably like to move to all sloping frames but I think there is still a decent demand for the traditional geometry from a lot of folks. But once we all die off, or demand wanes, I suspect you'll only see sloping frames being offered.
Like Lionel says, you can't really go wrong with your choice here. They are both far from the lightest bikes you could buy so I would base your decision on simply two things:
1) which one you can get the best fit on. I personally would be kind of between sizes on the Pinarello but sounds like you're on a Pinarello now, so that's likely not an issue; and
2) whichever one "speaks to you" the most. Unless you're a hard core racer and the bike is strictly a tool to get the job done, don't underestimate the pleasure you will get over the years from just admiring your fine bicycle, whether it's while your struggling up a huge climb or enjoying a coffee once you're at the top.
Fun times bike shopping.
I had a small chance to try them both few months ago... But i still cant choose becouse they had different wheelset (Colnago Had FastForward), and Pinarello Had Bora Ultra 35 (very stiff, but uncomofortable).
And Colnago was 48S (small for me ), and Pinarello even beeing 53cm (same as mine), was with all the spacers removed from the stem (i ride mine with 1cm spacer and plus conical headset cup, so i guess my position compared to that Dogma is 1.5cm higher).
Also i had injury (fall down from my Bianchi Pista 1 Month ago, and in the time of riding i was off the bike for 40 days (so not in proper shape) , and still a lot of pain in my arm, so couldnt say that i tried them properly).
From that test how i feel them at the moment:
Colnago C60: Not that responsive on climbing (maybe the wheelset were problem, maybe the small size), but very comfortable, and very stable on downhill
Pinarello Dogma: Very responsive, very fast on climbing (im not sure if that was result from the wheelset), but i got pain in my neck and i feel a bit uncomfortable.. Also nervous on downhill (still it could be becouse the stem was too low for me).
When i compared on Strava, i had faster time on Colnago (but i rode it Colnago First, and i was tired allready when i tried Pinarello after).
I ride them both for like 40km each
So ideal would be: Acceleration and responsivnes from Dogma, but beeing comfortable and beeing stable on downhill as Colnago.
So u now understund why im trying to get more suggestion on this forum..
The problem is that i cant try any of them again, and i need to order like this (i'll buy them from city 1000 km away from my place, and this is closest i can find them
), and also need to wait like 3 months from order
p.s. If any of u had a chance to try them with similar wheelset, i would really apreciate to share ur experience