All JS engines make different tradeoffs, so they are better at some things compared to other engines. For example, Chakra has had full asm.js optimization supp

All JS engines make different tradeoffs, so they are better at some things compared to other engines. For example, Chakra has had full asm.js optimization support for a long time now, while v8 still doesn't (but it's coming). We now have 4 high-quality JS engines that are cross-platform and open source (v8, SpiderMonkey, JavaScriptCore, and now Chakra). This is great!