Let me preface this with the fact I use Sketch-Up, Rhino and Aspire to do 3D designs, drawings and programing for a CNC router. In the end if I print or send the client a preview, it's still a flat image. It's still easier to draw in two dimensions than three. Ease of use is a very subjective term. So is price, because it doesn't include time spent learning. Free is sometimes worth what you pay for it!
"be able to print and show to prospective clients your concept"
If it's printed or on a computer screen isn't it still going to be two dimensional?