I moved from Photoshop exclusively, tried out Sai for a while, before I wound up with Manga Studio 5 exclusively.
(Kinda a weird journey... I'll explain)
I stopped drawing for a long period of time, about 2 years before I picked it back up two weeks ago. My Wacom tablet pen decided to run off without me and never reallly wanted to get a replacement pen, and previous infliction on drawings kinda put me off from drawing for a long time...
I tend to be exclusive to one tool at a time. Learn it, love it, and breathe it. At first, all my work was done in Photoshop. I used that for 4 years straight. I tried out Sai but I had weird interfierence with it and how it preformed with my previous Wacom tablet. It was jittery for me and the pen tools were odd to jump to for me from Photoshop.
-> Insert pen deciding to bugger off.
When I reformatted my computer, I lost my photoshop version (I lost the key... whoops.)
So no drawing for me for a long time... Two weeks ago my BF decided to get me a new tablet, and gave me a little extra to get a new art program.
So here I am, drawing on a Turcom tablet (Which I like much better than my Wacom o.O) and using Manga Studio 5. So far, I love how much -quicker- I am with MS5. Line art and the pen tools are intuitive to me, coloring is fast and I love that I have the power and quick tools of Sai, but the painting abilities of Photoshop.