I think the Sketchup from google is the best one for me to make a detail construction specially for the Hardscape. Also with a bundled progam called Lay Out you can organized the detail drawings easily from one source 3d sketchup file. And you can export it into dwg files.
I think sketchup is one of the easiest 3d software to learn. you can do the modelling in it really quick, and than if you want more photorealistic look you can trasport the whole stuff into a more expert program such as 3d studio max. i suggest vray for the rendering, it can go with 3ds max and sketchup too.
but if you need something just to do the modelling quickly, i would choose sketchup.
the choice mainly depends on how much time are you willing to spend on learning. the more popular software the more help-tutorials on the internet, which can help a lot.
These other packages are great but have you considered Vectoworks Landmark? I’ve been using it for over a year and the 3D modeling, grading and Landscape are far superior to Autodesk’s solution for a fraction of the price.