[disclaimer: I work on the Dart team]

I talked to our VM engineers, and they mentioned that the Benchmarks Game does not perform a warm-up before it runs the benchmark. This affects the Dart performance, because the Dart VM does not yet have on-stack replacement (OSR). Both Java and V8 have OSR so they perform better in the Benchmarks Game.

If you look at Dart's benchmark harness, https://github.com/dart-lang/benchmark_harness, you'll see that we perform a small warm up before we start measuring. It would be cool if Benchmarks Game did a warmup, too.

We plan to implement OSR but it's not there yet.