Sound: One of the most important things is that the mobile version doesn't have the online levels like the pc version. This is a real shame since you can only access original levels and there's not to many of them. Which of course means limited soundtracks that are really good.
Gameplay: It's easier than the pc version since you don't need to click specific keys but just anywhere on screen. If you're not familiar with the pc game version it's a rhythm game where you need to click at the specific time to complete the level along with beat and music.
Value: Is it worth buying? Personally, no. Even though it's cheaper it doesn't have online levels which sucks. As long as they don't add online levels I do not recommend buying this version but buying the pc one. Of course that's just my opinion. So if you want to buy it for example because you are skilled at mobile rhythm games and not so much at pc rhythm games or you just want to support the game dev, go ahead.