I've just bought a touring bike (Hewitt Cheviot SE) and have been comparing it to my road bike (Trek Alpha 2.5).
My comparisons have been a simple freewheel test down a local shallow hill and a ride around a 32 mile loop with 1100 ft ascent.
https://ridewithgps.com/routes/18854608
I initially found the tourer felt a bit sluggish. I was about 2 mph slower on the loop and on the freewheel test it went a shorter distance - hard to quantify in a meaningful way. It came with 32mm Conti Tour Plus tyres at 70 / 80 psi F/R. Max pressure specified is 80 psi.
I changed to 32mm Conti Gatorskin Hardshells and inflated to 80 / 90 psi F/R (Max is 102 psi) and on the freewheel test I went exactly the same distance as the roadbike on 25mm hardshells and 90 / 100 psi. I also regained my 2 mph on the loop. I think regaining the speed was partly due to me pushing the pedals harder, because I was enjoying the ride better. I'm quite a lump, 15 stone, so the additional weight of the bike was diluted by my own contribution to the cumulative weight. (I could have specced the Hardshells from the off by the way, I just didn't have the experience to know how much difference to expect).
Summarising, I'm pleasantly surprised that my average speed over the stated terrain is as close to the same that I can't tell the difference.
Hope this helps.
Graham