They have twice as many Twitter followers mate.
I know you will scoff, but its a decent metric in this day and age.
I mean why would people support Spurs over City?
Spurs will have a far higher number of match going fans etc City might have a fair number of arm chair fans around the globe, but very few of them would ever bother to make the trip to Manchester.
Spurs would take more fans to a match played practically anywhere, you'd get the a higher amount of armchair fans willing to see City in an exhibition game though in the US etc