I think it depends. LLVM is a very large project which adds a significant overhead to your footprint. LLVM also historically has focused on "normal" (i.e. AOT) compilation so is more concerned about generating good code even if it takes a while (which isn't the main focus for MS CLR, or Mono's JIT). LLVM have improved their x86 -O0 perf, but it's still not as fast as the fast path on JIT-focused backends.
So, yeah, there's a cost. Depends what the end user is using Mono for as to whether it's worth it or not I guess.
So, yeah, there's a cost. Depends what the end user is using Mono for as to whether it's worth it or not I guess.