This is where things get a bit difficult.
I know people love to compare compilers… But for instance, let’s take GCC and Clang.
GCC supports far more languages such as Go and Java, but Clang is much faster and consumes less memory. So, here we have a conundrum because for 1. there’s no way in hell you’re compiling Go with Clang and 2. you can’t dock points from GCC for being slower as it is built to the standards of several languages without AST support.
Comparing compilers for this reason is almost useless.
What you can compare however are optimizations.
For instance, a kernel compiled with Clang will almost without a doubt always be faster than one compiled by GCC due to how Clang issues optimizations.
At the same time, one compiler may be better suited for one driver than another thus causing slow downs if optimizations are discarded.
It’s Pandora’s Box. It’s not definitive. I can say X is better than Y for usecase Z, but I can’t say X is always better than Y.