I'm not aware that the demographic favors either young twinks or muscular guys, merely those younger than say their mid-forties.
The differing numbers in attendance may simply reflect the differing population levels, i.e., around 4 million in Taipei versus the 2.7 million in Kaohsiung. Taipei in the capital and more cosmopolitan and in many ways more developed than Kaohsiung, which is essentially a port city, and Taipei offers better job opportunities for younger people.