I guess it depends on what level of CNC you have. Milling and 3d printing are very similar in some ways but are opposite as you know. 3D printing is additive and milling is subtractive but a lot of the same principles apply to both. Milling can work on about any material and gravity has no effect. 3D printing can be time consuming in that there are more variables to manage, tweak and monitor. What prints perfectly today may not tomorrow. Milling machines pretty much just work. If you have sharp tools and a good jib, there's little to go wrong unless you mess up your cut manually. And, if you have a really fancy mill, you can just clamp your block to the bed and hit go and come back later.

I'd say that they both work out the same for the same kind of parts.