Points to be Consider1.Based up on Budget2.Requirement3.how much advance level you are going to use the Software based up on that you can buy the Add-on modules
some of the best software's and well known by mechanical Civil And Electrical Systems
Inventor (Autodesk- Vault)
Solidworks (Dassault Systemes- PDM)
Solidedge(Siemens-PLM)
Catia,(Dassault Systemes-PDM)
UGNX- (Siemens-Team Centre)
ProE- (PTC-PDM Link)
Choose best one which suits your requirement and one more thing all are user-friendly Software's
FYI : Best Market Competitors are Autodesk Inventor & Solidworks
i have worked with both software's both are pretty good and easy to learn
if you are looking for CAM ( UGNX & Catia )
other than those you have many cam software's
NC CAM
Delcam
MasterCAM
SmartCAM
Cheers :)