Years ago it was well-known that the Intel compiler icc was far ahead of others in the realm of optimization. Some massive speedups were reported when switching to it from other compilers, and it was quote clearly superior.
But in recent times the results have been different. gcc now produces code that's as fast as icc's if not slightly faster. clang isn't far behind. Even MSVC is catching up, though it has a ways to go still. Only with computationally intensive programs does icc still have a definite edge, particularly for floating-point code. Even that apparently is because icc uses "fast math" by default, whereas other compilers only do it if given a flag to enable it.
This is significant. Businesses could be wasting money on an expensive compiler because of misconceptions and outdated information. I suppose consumers too, but icc is generally more of a commercial product. There's some suspicious things about icc too, like how it compiles a slow version of the code and executes that on non-Intel processors, thus making them appear slow.
There are still cases where switching to icc gives a massive speed boost. But nowadays the opposite is just as common.
Edit: I just found out that the Intel compilers are free now. That probably says something about its standing.
there doesn't seem to be anything here