I think to separate the two misses the point entirely with respect to what Steve -- and Apple -- is all about. This is why I selected "both equally."

Steve's vision for Apple -- and the products and services they have produced since his return -- prove that his passion is the "sum of all parts," i.e., the whole package of hardware, software, UI, services, etc.

Apple's software, minus the second-to-none hardware design, wouldn't be Apple.

Similarly, Apple's stellar hardware designs, minus the phenomenal software and UI, wouldn't be Apple.

So if I were to pick a singular answer to describe Steve's passion, it wouldn't be "hardware and software equally" but rather, "the end user experience." That's his passion.