I wouldn't advise photoshop for digital drawing to anyone (mostly because of the current subscription model but also because it's a photo editing software with bunch of stuff added to it and let's be honest, you'll most likely not gonna use most of it) unless you'll going to look for a job in digital art, as that's what most companies use.
Sai, at least the original sai, not sure about the sai 2, is quite bare bones but it's got very intuitive brushes and the curve tool can be really helpful, especially if you don't have a drawing tablet.
My software of choice is Clip Studio Paint - a great middle ground between photoshop and sai, that is being constantly updated with new features, has a lively community and a marketplace with bunch of free assets.