If I buy the PC version, I am pretty confident that I will get a pretty much identical game to the console version, with at least equal if not better graphics. The main issue with console ports of games like Final Fantasy is usually that they don’t always create a new control scheme for stuff like inventory management, so you need to push a lot of buttons to go through sub-menus of sub-menus instead of using easier mouse + keyboard controls. That can be somewhat annoying, but is not really a serious downside. So I’d consider the PC version a conservative bet.
The mobile version, called the “pocket edition” is going to be released next week, February 9, and is conceptually much more interesting. Because in this pocket version they tried to reproduce the game as faithfully as possible on a platform which is both much less graphically powerful, and has a much more different control scheme. But people who saw the beta version were astounded how faithful to the original at least the start of the game is. Basically you see the same scenes, but with new graphics which are far better suited to the lower resolution and capabilities of the platform.
There have been a number of games in the past that were re-released with improved graphics, due to the constant increase of computer graphics quality. The reverse process, down-grading graphics to lower resolution, hasn’t been used that much. But of course the concept is very interesting if you think of porting games from the PC and console to tablets and phones. So I am definitely going to check out the Final Fantasy XV pocket edition. Especially since I don’t need to buy the full game to do so: You get the first chapter for free, and can buy the rest of the game chapter by chapter. Now that is an innovation I wish would apply to console games.