I I can only report my experience with 3rd Planit; I never used Cadrail. I found 3rd Planit difficult to use; in particular I was not able to get track alignment to work. On the other hand, I downloaded SCARM = simply computer aided railroad modeller for free and found it to be very easy to use after watching a few YouTube tutorials. That was earlier this year, 2015. Since then I have designed several different track plans for which I hope to use for a future home layout.
I have never used 3rd Planit...I use Cadrail exclusively....I've been using it now since it first came out so I'm pretty familiar with it. Learning curve was a little steep, but not overly difficult, especially compared to actual industrial CAD programs. I use it not only to design my trackplans for my modules, but I also design the woodwork/benchwork on my modules, setups, and weapons-mountable night vision devices and surveillance cameras with it. Works okay for me. It's really great to be able to know within a thousandth of an inch or better how to make stuff....it's saved me a LOT of headaches over the years! I've heard good things about other model railroad CAD programs, but since I already know how to use Cadrail and it works very well for my purposes, I haven't wanted to take the time to familiarize myself with the others. Bob Gilmore
Many modelers, including myself, have had good luck with XTrackCAD, another free program that does an excellent job. It costs nothing but your time to give it a try. Their Getting Started section is very helpful. http://www.xtrkcad.org/Wikka/HomePage - Jeff
Again, I assure you I have found SCARM very easy to use and it is a free download. On YouTube there are 4 or 5 basic tutorials, that I found very helpful. The choices for n-scale track templates is very extensive. I have designed several track plans using Kato Unitrack complete with their turntable, track plans that combine Kato Unitrack and Atlas True-Track, and one that used the Walther's 130' turntable. I like the 3D feature of being able to view the plan and/or structures that can be added. For all of the plans I have created, I have made the assumption they would be on two inch thick extruded polystyrene foam. This is done by setting the track height to 2". The software allows one to create streams and ponds that are below track grade and to add hills or mountains well above track grade. Certainly the price right, so if one wishes to try it, they can and learn if it meets their needs and expectations.