
I do recommend getting it from the Japanese dev as Clip Studio Paint, however, as Clip Studio Paint gets updates more quickly than Manga Studio 5, and you're directly supporting the developers.

To top all of this off, Manga Studio 5 also has the best support for touch and tablet pc's.

Manga Studio is also the only one that will give you (almost) all of the necessary stuff from photoshop if you're planning on taking advantage of many digital-only techniques (Adjustment layers, gradient maps, etc). Frankly, I even prefer it over photoshop, as the color mixing brushes are actually usable without insane amounts of lag. Manga Studio's brush engine surpasses pretty much everything out there. If you're only getting ONE of them, I'd definitely recommend Manga Studio 5. I've used almost every program out there, and spent several months trying to find what best fit my surface pro 3.

Here's a wall of text, detailed answer for you.
