My DAW of choice is Samplitude Pro X Suite... but, I also have Presonus S1, Avid Pro Tools ( 8), Sonar PE (8) and Harrison MixBus, so that I can cater to various clients and their preferences.
But, if I'm doing something of my own, or if a new client comes to me and wants to start a project, and they have no particular preference, I use [="http://www.samplitude.com/en/"]Samplitude.[/]
As for the reasons why, there are far too many to mention here - other than to say I love the Object Based Editing feature; and also because I find Samp's engine to be highly accurate with audio playback.
I don't want to start a debate by that last statement.
Let's just call it a personal observation/preference, based on my own experience with many of the other popular DAW programs I've used over the years, and leave it at that.
I have S1 2 Pro and I love it. It takes me from tracking to mastering for CD mfr/digital release. I dumped Cubase about 4 or 5 years ago and never looked back. Thought it was OK, but way happier with S1 after I got it.
Did some Sonar before that, but I haven't touched Pro Tools since the 90's and never really seen or used Reaper or Garage Band.
Mixcraft Pro Studio 6. Programmed by musicians for musicians, powerful, user friendly and super affordable. Plus extremely timely and responsive tech support, when it's called for. Constant upgrades. I love it!
I used Sonar for a year it was a decent DAW with a wealth of great synths. The only thing I didn't like was having to bounce between different windows. A few people told me about reaper I checked it out on youtube and am now considering it as an alternative. Protools wants you to do a ton of routing...I guess trying to mimic an actual studio.
PT 10 w/production tool kit here - no better than any other DAW. That being said I'll never upgrade to newer version since avid decided to stop supporting my (pro control) control surface. I've tired Reaper but didn't really liked it but there are a lot of people who do - just not my personal choice but the price is hard to beat.
I also have an analog console and I'm currently looking at the Orion 32 which would give me option of upgrading PT but I've grown very fond of the complete recall capability of using a control surface.