have you thought about skimming the sw threads for the polls from the past and using them to create an overview of opinion over the last few years?
to help you immediately I use Cubase 5.5.3, Reason 4-8.1, reaper, pure data, finale notepad, musecore, MCMusicEditor (An ABC editor with postscript, pdf and mid capabilities), BiaB2012, Komplete 8, Audacity, several other nameless vsts
the whys are many but all relate to their specific usefulness for particular work routines