You're not entirely wrong in your assessment of the two cities, but I would say that's a pretty highly subjective assessment of how young players with money in their pockets might view living in both. Melbourne may be a more bustling and cosmopolitan city, but it's also a long way from home for guys who might have been born and raised in Queensland or even NSW.
The anonymity and the 'bubble' environment of living in Melbourne suits some guys down to the ground and many young guys absolutely thrive in it, but for many others the desire to be closer to home and around your family and mates would easily overcome the less cosmopolitan feel of living in a city like Brisbane. Footballers have a mountain of spare time on their hands given the relatively few hours of 'work' they actually have to do, and just as I'd agree that for some guys the nightlife of Melbourne would be a huge drawcard and the bubble environment of living and socialising with predominantly just you team mates is not an issue, for many others all that free time and cash is not worth all that much when you're 2000 kilometres from the people you know and love and would like to spend it all with.
I certainly can't speak for Grant specifically, but to presume that all or even most players would definitely view either city one way or the other is frankly being a bit presumptuous and perhaps imposing your own preferences over the whole thing instead of the reality.