In practice we don't think there will end up being tradeoffs in async2 vs. async1. If you look below, at the "JIT state machine" section, you'll see that async2 looked better and the GC behavior differences were probably transient.
Overall, there are no architectural reasons why the compiler version should be better. The runtime should be able to make perf decisions that are at least as good in every case.
Overall, there are no architectural reasons why the compiler version should be better. The runtime should be able to make perf decisions that are at least as good in every case.