I have both autocad and pro landscape. Pro landscape is great for quickly putting in a house and then dropping in standard plant symbols. Its photo imaging is nice as well because you can drag graphics of certain plants into a photo of the house and have a rendering to show the client in half an hour. But, the labeling in the planner software sucks, and the images of the plants show them in bloom. Well all plants don't bloom at the same exact time, so its not an accurate way to show the clients what it will look like after you have finished the job.
When I use pro landscape for a plan view, I still use autocad to label it. It's just easier for me this way. Autocad is completely customizable, but if you don't have a library of already made symbols then you won't be productive trying to use cad. You can go all out and purchase autocad/ land fx but you're at a couple thousand dollars for those two pieces of software.