[EricBurnett]

The differences between bazel and BuildXL are less about platform and more about philosophy. Bazel is about opinionated builds - declare everything, and you get fast correct builds. Hard to adopt, but super powerful. BuildXL is more about meeting codebases where they are - take an existing msbuild|cmake|dscript build with its under-specified dependencies, and figure out how to parallelize it safely. This delivers quick wins, but comes with real costs as well (notably: no caching; labour-intensive magic to guess an initial seed of deps, with a performance cliff when something changes).

(Disclaimer: Googler, work closely with the bazel team. I like bazel; I like BuildXL for expanding the space of build ideas, but have long-term concerns it settles in a local maxima that'll be hard to get out of).