SAI is my go-to. I prefer its brushes vastly over anything Photoshop has ever offered, they simply feel more natural to me, and less like rubbing a stamp around. I do all of my work from sketching through to colouring in SAI, hopping to Photoshop only for postwork if I feel there's a need. SAI also runs much smoother and lighter than PS for me, which my laptop greatly appreciates.
That last sentence sums up my reasons for thinking about picking up PT Sai. The time spent learning and adapting could be time spent creating new pieces in Photoshop but if the device you're working on cannot handle PS as well as you would like, well, it's a no-brainer really! Plus as you say, it has a different feel to it and change isn't necessarily a bad thing.
Well, I use both and I do exactly what you say. Drawing, sketching in PS is simply a pain because it gets laggy (due to my 4 years old laptop) so I use PaintTool Sai. Photoshop is what I use for applying text, or the many layer styles and preferences it can offer. But that's only after I have my lineart clean and coloured!
Why specifically for older computers, is the sketching and line-art that bad in Photoshop on slower devices?
I have a Toshiba Tecra M7 on the way, a convertible laptop-come-tablet from 2006 but it has been upgraded a fair amount to compensate. Been told Paint Tool Sai should run beautifully although Photoshop seems to be a case of finding out the hard way. As long as it doesn't lag my lines to the extent of having curves appear jagged I will be happy.
I have seen that , in my computer, there is delay between the actual stroke of my pen on the tablet and its appearance on the PS workspace. It all depends on the resolution of the document you are working on, though, always talking about PS.
All tablets have that (there is a term for it but I cannot recall the name). I don't mind the lagging behind as long as it follows where I was pressing on the surface. The problem comes when it lags behind and doesn't follow the arc, instead going for a "shortcut" and not following the path of the pen.
I guess an example would be drawing a circle. With a delay that still follows the path it would come out like a "O" but if it delays and doesn't follow the path then it could look more like a "D". It might vary depending on what programme you use, I don't know. One of those things I have to try out.
You can easily do everything you need in photoshop. You dont need to switch different programs for painting. Photoshop you can do anything as long as you know the correct tools to do it. I do everything in photoshop start to finish and i dont feel the need at all to jump into a different program to finish something i was doing in ps. When i paint its 100% photoshop, dont need another program to aid it. Just learn more about photoshop and you wont have this issue.