Your Preferred Software for Creating 3D Models?

For organic, clay like modelling, Sculptris is hard to beat. It allows you to create very fine detail on a model surface because it increases the number of polygons automatically in critical areas. One has to use this feature with caution though because you can easily create millions of polygons this way. I do my models as high res as I wish and then decimate them using either the built in routine or something like meshlab. You lose some resolution but with a little experience you will know what the printer can reproduce. The upgrade on this if you find this kind of modelling to your liking is ZBrush. Another strange interface...but one can do great things with it.
For drafting and precise dimensions I use the new Cubify Design. Basically its Alibre/ Geomagic Design minus some functions I dont need anyway. To me the best interface for a beginner/hobby user. It educates you because it forces you to be precise with your sketches and dimensions.
I also use Rhino 5 but find the interface leaves a lot to be desired because it comes from the " stone age" of CAD with its tedious command line structure. I also tend to forget many of the tricks and have to start from scratch after a few weeks of non- use. And once your model is built, that's it. You cannot modify it anymore, so you either have to tediously save each and any important step or you will bite your fingernails later on. But the freeform NURBS functions are fantastic.

Same goes for Blender, that is extremely powerful but very hard to use. In Blender I have a real problem with dimensions since it is not made for CAD but for freeform modelling. Again if you use it everyday it will become second nature, but for the intermittent user its interface hell. Many of the more interesting functions can only be reached thru keyboard shortcuts and I cannot remember them at all!!!!
3ds Max is super because it is also history based, and it has these great boolean functions that allow you to access all of the original parts that make the boolean object even after you have built it. But its another league of program, very expensive....
The free version of netFabb is also a great accessory tool. I use it to cut up models that will not fit into the build area of the printer, and you can reverse surface normals, cap holes and do other basic repairwork you may need.
Generally I can only advise anyone who wants to buy or build a 3d printer to get a software workflow down before you start. only if you know the steps from empty screen to finished g-code file by heart you will be able to unleash the true power of 3d printing. I played around with all these various steps for more than a month before I ordered my UltiMaker machine. Now I have two of them and they run almost every day. Science Fiction World, really.