Is there a good reason to ever start modelling with something other than a subsurfed cube? I have concluded that starting a (reasonably high poly) model with a subdivided cube is always better than anything else. Even if I have to model a pipe, or a cone a cube is the better choice.

In the case of the pipe, if I start with a cylinder I have to commit to the resolution from the beginning, since Catmull-Clark subdivision doesn't work well on it and simple doesn't preserve curvature. It's also harder to create bends than with a subdivided cube where a single 45° loop makes for a nice 90° bend.

In case of the cone, the inability to create edge loops is enough to make the subdivided cube a better proposition.

The spheres have one or both of the above disadvantages depending on the type and orientation.

I have little experience with torus-like objects so I can't say anything about them.

Is the above conclusion right? If not, please explain why, or in which cases it is better to start with which primitive.
UV spheres are good. If you subsurf a cube until it is smooth, you will get a spheroid, but, not a perfect sphere. To get a perfect sphere you must start with a sphere.