With Cubase or Nuendo you don't have to buy overly expensive and poorly made proprietary gear which you don't need or want. With Pro Tools you do.
Cubase and Nuendo are very good, fully capable sequencers, as well as DAW; Pro Tools has crap for MIDI sequencing. Professional Pro Tools users use something else for sequencing.
I have not used a current version of Pro Tools in about 5 years, but my Cubase SL is much easier to work with than Pro Tools was back then.
Neither of them have really great mix busses, but no software mixer does, so that is a wash between them.
Personally, I want to get Nuendo with a pair of Apogee AD-16Xs (when they comes out). You can hook up one of the finest ADC's on the planet direct to your computer, 16 channels each at 192k, over firewire. No more expensive and low quality sound cards for me, thank you very much.
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M.K. Gandhi