What do you mean by "plan sets"? Construction documents? If so then either program is quite capable of putting out whatever it is that you create. Not going to do it for you so you are responsible for the content and appearance. With that said it is my personal belief that Softplan is easier to work with as I do a lot of details and Softplan gives me tools that don't exist in Chief. I don't expect any program to be able to fully comprehend what or how certain things go together so the need for 2D detailing is critical. I get what I need with softplan but the bottom line is that I have to be responsible for understanding how to build something and the subsequent details.
Your comment that "Chief wins as far as learning curve and renderings" isn't necessarily accurate. Chief is very easy to use right out of the box for "basic and simple" stuff. Start trying to design any complicating aspect and you will find very quickly that you have a whole lot to learn before you will be successful. Not a bad thing but it is the truth. Similar things will occur with Softplan but that subsequent learning curve is shorter- and easier in my opinion. Your opinion may vary.
As for the renderings, well, beauty is in the eye of the beholder and the skill level is subject to the individual. I know what Chief can do and I know what Softplan can do. I use Softplan,