100% on the team making the most difference. (An aside: a software project I've been admiring recently is the Apollo Guidance Computer's. To the moon and back on a 15-bit 1s complement machine and a few kb of memory. It's a case where the team was certainly better than the available tools.)

On the perf side: I'm curious to know where Go sits now relative to C assuming you elide away all heap allocations in your inner loops. In the early days Go's codegen was based on plan9's simple and simplistic C compiler's back end. Things have gotten much better since then and to my knowledge it's within striking distance of C. But I could be wrong.