Before you commit to buying any landscaping software try to get a demo. This will let you try out the program to see if it can even help you in what you want to achieve. You should try to choose a landscaping software program that has good graphics. The better the graphics are on your landscaping software the easier it will be fore you to visualize the end result of all your hard work. Remember that this is the goal of any landscaping software program. If the landscaping software is crap then you might be better off using the drawing programs that are already on your computer.
By getting a demo you will also be able to directly compare the different programs in terms of price. Lets face it, if there are two landscaping software programs and they look the same and they both have the tools that you need but one is cheaper, which one are you going to chose? The cheaper one of course. So check out the prices.