A lot of it has to do with comfort and familiarity. I can work quickly and accurately in Illustrator, but for me the biggest thing is I can have a huge canvas running in Illustrator at a fraction of the file size it would take in Photoshop. This means it takes no-time to open and save files and for the screen to redraw as I chop and change linework. Then, once I am happy that my drawing is as accurate as I can make it, I progress to Photoshop.
Photoshop is a great package for what we are doing here. It does have most of the path creating features of Illustrator and it can be incredibly precise. Don't worry about those people who claim Photoshop is purely a photo-editing package. It is incredibly powerful at that work, and that is where it all started, but it is also a sensational creative tool.
I have a friend who draws Fairy and fantasy paintings and he swears by Painter. That appears to be best for really loose, expressive stuff, but I haven't even looked at it.
It has been suggested to me that I might do some screen grabs and post my progress through the Illustrator and Photoshop phases showing the way I use the two. Is that something that would interest people or would I be preaching to the converted?
Let me know your thoughts.
All the best, Grubby.