Agreed, comparing functions in isolation can give you drastically different results from the real world, where your application can have vastly different memory access patterns.
Does anyone know how well the JIT/cache on the browser works eg. how useful it is to profile JIT'd vs non-JIT'd and what those different scenarios might represent in practice? For example is it just JIT-ing as the page loads/executes, or are there cached functions that persist across page loads, etc?