I avoid closed-source tools as much as possible. But sometimes they happen to be the most performant choice. I've seen the claim that the Dyalog APL is the fastest, for example. Commercial compilers from chip manufacturers (Intel, e.g.) are popular for numerical applications, as the free alternatives, excellent as they are, simply can not make the detailed optimizations that the targeted compilers can. The chip makers invest in developing these compilers because they make their systems look fast on benchmarks.