The storage industry is considering new kinds of storage devices that support data access function offloading, i.e. the ability to perform data access functions on the storage device itself as opposed to performing it on a separate compute system to which the storage device is connected. But what is the benefit of offloading to a storage device that is controlled by an embedded platform, very different from a host platform? To quantify the benefit, we need a measurement methodology that enables apple-to-apple comparisons between different platforms. We propose a Media-based Work Unit (MBWU, pronounced "MibeeWu"), and an MBWU-based measurement methodology to standardize the platform efficiency evaluation so as to quantify the benefit of offloading. To demonstrate the merit of this methodology, we implemented a prototype to automate quantifying the benefit of offloading the key-value data access function.