No, it's strictly better than both. You get the performance of local storage and the ease of programming of central storage.
Pretty much everyone chooses central storage at the moment, so the advantage of mobile objects manifests as performance.
I don't know about you, but I would find it a much nicer experience if when I clicked "Add Item" in a shopping cart on some website, it happened <5ms regardless of the quality of my network connection, while still being shared between different machines and never encountering consistency issues. The current "wait somewhere from half a second to several seconds for each click" is bad UX, even if users have gotten used to it.