I mainly use Clip Studio Paint because its function as a painting tool is much better than other programs I used. But I also think Photoshop is good in terms of effects and stylizing artworks. In short:
Clip Studio Paint: Good if you know how to paint in real-life, and want to do a high quality artworks for comic. Other than that, it has a good manga-like features that you could use (speech bubble, creating frames, action/movement linework, etc)
Photoshop: Good if you know how to create your own brush (or download/use brushes). You could do so much with Photoshop if you know how to. So it's kinda like a wild card.
Sai Tool: I only used it couple times... It's function as a painting tool is somewhat between Clip Studio and Photoshop. But its kinda like.... there's limit to what you can do? It will create the same pixiv looking drawings... so I don't recommend it if you want to do drawings/paintings professionally.