I really like the stabilizer feature in sai, plus it has most of the useful tools other programs have. I wish I could type in it tho, and I miss some filters and everything from photoshop, so I switch back between sai and Photoshop if I need to do something that Sai can’t handle.

I tried Manga Studio, too, and I liked it, it has some very interesting features but in the end I was too comfortable with sai to change. I personalized my sai a lot, pretty much all the brushes are individualized, I put a lot of time into arranging hotkeys, settings and everything. I’m very comfortable using sai, and I think that’s the most important thing about choosing the tool of your trade.

It doesn’t matter too much which program you chose, what matters is that you can make yourself feel comfortable using it. And I’m sure a lot is just getting accustomed to the program. I don’t think any program is inherently better than another. But it helps that sai has the great stabilizer and a lot of convenient features and is relatively cheap. I think that’s what makes it popular. While photoshop is amazing and does great things, most of its features won’t be needed on a daily basis by the average artist.

I hope I could help!