Which is grammatically correct Simpler approach or more simple?

Both "simpler approach" and "more simple" are grammatically correct, but they have slightly different meanings and uses:

* "Simpler approach" emphasizes the method or strategy being simpler. This is more commonly used when discussing a process, plan, or technique.

* "More simple" emphasizes the degree of simplicity compared to something else. This is more commonly used when describing a quality or characteristic of something.

Here are some examples:

* "Simpler approach": "Let's try a simpler approach to this problem."

* "More simple": "This design is more simple and elegant than the previous one."

Ultimately, which phrase is more appropriate depends on the specific context and what you want to emphasize.