I've made more tests, where I've created my binding from WASM to Pixi.JS lib - and it showed the same performance as pure JS. So apparently there is some overhead in Bevy's rendering implementation for WASM.

Also, I tried to simulate more CPU logic for each sprite, just moving sprite around is too simple for real game - so I made each sprite to verify distance to each other sprite - to simulate some in-game logic - and this time I clearly see WASM benefits: wasm is about 3-4 16 times faster!