So, back in the Designer, and some solid numbers.
12, 36 and 48cm straight ducts count as 3 points of cable allowance.
72 and 96cm ducts count as 4 points
144 and 192cm ducts count as 6
Intersections are 3 or 4 points.
2m of either pipe or cable costs 20 (twenty; two-zero) points. Laying both across the same distance uses 40. It's 10 bits per "nominal metre" and you have to count twice if you want both services. Duct is definitely more efficient in budget terms than laying 'loose' cable and pipe. There are probably edge cases where, if you only want cable, (only wanting pipe is pretty rare, I reckon), you might shave a few points off by getting the pipe tool out. And it's easier to drive a pipe and cable through things that are in the way. But mostly, your backbone should probably be duct, at least as far as build budget is concerned.