Years ago I was surprised when discovered that Intel sells Studio compatible compilers. I tried it in particular for C/C++ as well as fantastic diagnostic tools. But the code was simply not that computationally intensive to notice the difference. The only impression was: did Intel really did it for me just now, Wow, amazing tools with nanoseconds resolution, unbeleivable. But the trial ended and team never seriously considered a purchase.

From your experience, if license cost does not matter, which vendor is a winner ?

It is not broad or vague question or attemt to spark a holy war. This sort of question about 2 very visible tools. Nobody likes when tools have any mysteries or surprises. And choices between best and best are always the pain. I also understand the "grass greener" argument. I want to hear all "what ifs" stories.

What if Intel just locally optimizes it for the chip stepping of the month, and not every hardware target will actually work as well as Microsoft compiled ? What if AMD hardware is the target and everything will slow down for no reason ? Or on other hand, what if Intel's hardware has so many unnoticable opportunities, that Microsoft compiler writers are too slow to adopt and never implement in the compiler ? What if both are the same exactly, actually a single codebase just wrapped into 2 different boxes and licensed to both vendors by some 3rd party shop?

And so on. But someone knows some answers.