Size matters. The difference between the two will be the run times. And the higher capacity Spinner will be correspondingly larger. (Longer in this case.) As a very rough guide, every 100 mAh in battery capacity translates into 1 hour of use between charges. What you need at that point becomes a matter of personal preference regarding the actual size of the battery - some people prefer a smaller size, other people don't care about the size if it's going to provide a longer run time between charges,