The feature set for one. I know there are many choices for DAWs and they all pretty much have or do similar features but for me, the workflow, the stability of the application and the "quality of the sound (I know very subjective)” I’ve gotten out of Samplitude is why its my personal choice. I'm sure others have the same feeling about what the use as well.
I don't believe it does everything the best but then again, I don't think any DAW does "everything". I record mostly audio with limited midi applications and the program has been a rock solid performer on limited PC hardware.
I will also say I had considered Pro Tools at one point but that application comes with limited track counts (albeit, you to buy additional capability) but worse than that (IMO) it locks you into specific hardware. I chose to go with Samplitiude Pro and have had no regrets.
Here’s a link to some tutorial vides if you’re interested.
http://www.samplitude.com/en/community/tutorial_videos/introduction.326.html