And to be honest I vote 15mm because that is what I settled on.
I long considered 1:35th/54mm due to the amount of modeling support it has. but then I started pricing model vehicles.
But really it is the choice of the players in your crowd. My crowd does 15mm mostly because I started collecting it and no other reason.
As another point in favor of 15mm ease of painting for the table top, there is no where near the detail on your average 15mm figure that there can be on your average 28mm, so painting is streamlined.
But if you do a lot of conversions 28mm is so much easier.