iDevice Vertex vs Pixel Shader Performance

Does the performance of the vertex shader affect the performance of the pixel shader? Specifically, if I am fragment shader bound, will making my vertex shader twice as fast help or have no change? I ask because I gather some platforms share execution units between vertex and pixel shaders, so the two are interrelated. How do they relate on SGX?

Given that SGX+ devices use a unified shader architecture , it should.

You just have to keep in mind that more often than not, there are a lot more pixels to be shaded than vertices to be transformed and thus any savings within vertex shaders won’t necessarily make huge difference in terms of how fast your fragment shaders run.