Depends what im doing

I record in the studio using Pro Tools and the digi002
I write loops using FRuityloops as its great for that
I use Ableton when playing live or recording live from analog stuff like my monopoly as its easier to remanipulate the audio
I write full tracks for techno/dance etc in Logic Studio 8
I've used cubase many times and occasionally like to sequence audio in it due to the inplace VST fx feature which is mint.
Reason i use to teach synthesis and sampling in composition or computers and music units at work.