ive used ps and sai and like sai a bit better, personally. photoshop is hella powerful, but i like sai a bit more because its more lightweight, faster on my machine, and the stroke correction is always a plus. painting and blending in sai is pretty nice, but i dont really paint much, so w/e.
there are some annoying limitations though, which is why i sometimes just bounce my sai project to a photoshop one and work from there.
blooop Still working on it

also, very rad