Good question! Pure JS would likely be comparable or slightly faster for this specific test since there's zero interop overhead. The 10k rectangles benchmark is specifically testing the interop architecture (Emscripten's glue vs. my command buffer), not WASM vs JS performance.

The real advantage comes when you have compute-intensive operations, data processing, image manipulation, numerical algorithms, etc. The batched command buffer lets you do those operations in WASM, then batch all the rendering commands and flush once, minimizing the interop tax.

For pure "draw 10k rectangles with no logic," JS is probably fastest since there's no bridge to cross. But add real computation and the architecture pays off :)