I have BMC pro road race bike from 2003 and bought a steel CX bike for commuting a couple of years ago. Commute is about 22 kilometers with some small and more or less straight gravel sections (only couple of 100m) and about 300 hm in total.
I bought the CX bike as a frame set and built it up as a "full commuter":
- Mud guards front and rear
- Front hub dynamo and good front and rear light
- 25mm continental 4 seasons road tires.
I started doing the commute in the summer on my road race bike but once it started to get colder, darker and wetter I built up the CX bike and since then only used that one.
The CX bike is a actually not a real CX bike. It is marketed as a CX bike but it is actually an adventure bike. It is a steel Genesis Croix de Fer.
It is much heavier than the road race bike (7kg vs 12 or more).
Yes the road race bike feels lighter and is a dream to ride on nice roads, however the difference is speed is very small. I've used the CX for road cycles with friends as well and it was ok. I might not choose it for a race day (not that I have any).
I did the commute for about 2 years, now I changed jobs and only have a 3km route on cycling paths. I use the commuter.
Now in autumn I sometimes go out for a 30km road ride in the evening when it is already dark. Obviously I use the commuter. It's great for this "training" purpose.
My CX bike with the steel frame and fork, the lights and other commuting spec is very heavy but still a fast ride - just does not feel as nimble as a real road race bike. The tires make the biggest difference in ride feel. Road race tires on a CX bike - it will feel alot like a road race bike.
Bottom line is that a similar spec Road and CX bike will feel similar and for an allround commuter and road bike I would definitely go with the CX.
I didn't necessarily want disc breaks but the bike I wanted only came with disc mounts. So I went for mechanical disc breaks which I clearly do not recommend. At the time the step up to hydraulic breaks was nearly 500 Euros (ultegra 11s hydraulic group instead of 105 10s mechanical), so it just wasn't worth it for me.
If I ever need to replace the sifters, I'd upgrade to hydraulics without looking back.
The mechanical brakes work, but feel very slushy, don't have a lot of power (actually worse than a decent rim brake). I tried different discs and pads but the performance was below average.
Sorry for so much text,
CX bikes a great. Use them!