Cubase VST/32 5:
MIDI programming/sequencing, scoring, audio recording, VST host (for software synths and modules)
Cakewalk:
MIDI programming/sequencing, scoring, audio recording (less efficient than Cubase, but requires less power tu run)
Rebirth 2.01:
Standalone authoring environment featuring software emulations of the following machines:
Roland TB303 bassline (x2),
Roland TR808 Drumatix,
Roland TR909 Drumatix. Additionally, it features the following modules: pattern banks, song builder, distorsion, compression, PCF (filters).
Acid PRO 2.0:
WAV sequencer, arranger. NOT a composition tool. You import WAV loops you create in other programs (Rebirth..) or with your other synthesizers, and you put them togehter. Acid matches the loops beats together, tempo, and all that. AGAIN, Acid is not a tool to "compose music" but it is a great WAV sequencer, useful to create a remix of your own songs.
.... long post!
this will help you
see you around