I imagine they've improved the runtime size since that stack overflow post was posted a few years ago. However I've never used dart and just tried it out using a basic html sample from the tutorial page and I see:
264 Mar 5 12:21 a.dart
237K Mar 5 12:21 a.js
101K Mar 5 12:22 a.min.js
It was also slow to compile, 6 secs.Anything I'm missing?