Well here's my statistics from Veloviewer.

I've done around the same distance and time on both my DS and my CX bike. Now I know the CX isn't a performance road, but it's drop bar and about 5-6 kg lighter. Both bikes have been used for a mix of commute, short ride, long ride, dirt, trail..... Not a big difference in average speed (1.6kmh) , AND I've been fitter while riding the CX rather than when I was a complete out of shape newb on the DS originally.

What's my point...I dunno, just an observation I just ride