It depends where you are running the code. The Ifor compiler has optimizations for Intel processors, so it would run faster in those systems. But on a different CPU it wouldn't be able to take advantage of the optimizations made for that CPU. I don't know if it would run slower than gfortran in, say, an AMD CPU, but if you have Intel hardware, and access to the Intel compiler, that would be the best choice.

i will recommend u to use Ifor compiler because i run faster than the other compiler and i have experienced it alot.