The reason I recommend Autodesk Inventor to drafters in the UK Building and construction industry because It plays pretty nicely with AutoCAD. But don't take my word for it, check out this article and the accompanying Videos by Garin Gardiner of the 'In the Machine' Autodesk manufacturing Community Blog...
A.U.G.I – The Autodesk User Group International is the official user group for all of Autodesk's products. It is sponsored by Autodesk (amongst others), but it is independently run by volunteers and is Free to join.