What are the differences from 3D printing View and from your practice experience between

Blender - DesignSpark - Sketchup

my four objectives:

  • quickly to complete 3D Design - from simple to complex 3D Design
  • for free and have a lot of user (which using the program for 3D Printing)
  • good interfaces (import and export)
  • ready for the future (reasonable development)