It's also important to consider how often the GC runs. GC that runs in 200us but does so ten times within a frame deadline might as well be a GC that runs in 2ms. Then there are issues of contention, cache thrashing, GC-associated data structure overhead, etc. The impact of GC is a lot more than how long one pass takes, and focusing on that ignores many other reasons why many kinds of systems might avoid GC.