Why does this person have such negative views of GCC and positive bias towards LLVM?
Seems to have a decent amount of knowledge in this domain in education and professional work. Author is from MIT so maybe professors had a lot of influence here. also, gcc is relatively old and comes with a lot of baggage. LLVM is sort of the defacto standard now with improvements in performance
Distributions, and therefore virtually all the software used by a distribution user, still generally use gcc. LLVM is only the de facto standard when doing something new, and for JIT.