Here's a link to the basic specs of the game. It says nothing about the performance of the game in an iPhone 4S. However, if you check the comment section at the end of the page, a lot of users are complaining about crashes in the game.
As an iOS developer, I can tell you that most frame-rate drops and slowdowns happen due to poor optimization. And most of the time, the crashes happen due to poor memory management or random bugs in the code.
This is pure speculation, but given that this is a ported game, it is quite possible that many sections of the code are not optimized to work well on iOS.
Having double the processor speed in the iPhone 4s is going to do little to alleviate these issues. It just might help the game to keep more stable FPS or load quicker.
The only way I see for this game to run better in iOS is if the developers release a patch to fix bugs and optimize the code.