For midi I use Sonar (I started with Cakewalk 2.0)
For audio I use cooledit pro.
(started with cooledit96)

One of the reasons you might choose for Sonar could be that there are lots of instrument patches with all midi definitions in it.
Saves a lot of time. ( It's a lot of work to write your own..)

When I started with cooledit pro I was on Cakewalk Pro audio 8.0.
Somehow I never got used to the audio capablilites of CPA(very limited) or Sonar (better but still limited), Cooledit pro has everything you need with very limited processor use, so that leaves you with a lot of extra tracks without latency.

Fred