i am a beginner at 3d modeling and am using rhino3d. i tried the simple software like 123d, tinkercad and even a bit of sketchup, etc and found them to be easy IF you wanted to design something simple or easy but they all seem to be limited and to do anything you want to do they become difficult because of the lack of tools. i find rhino to be somewhat easy but also extremely powerful. lets say its easy on a professional level. i bought myself a video training course on it and that was enough to really get me rolling with it in no time.