Literature from Operations Research would suggest that the change in structure should benefit the stronger teams. The actual data would suggest that this might also be the case. Figures 1 through 3 provide the cumulative distribution of the All-Ireland winners, finalists, and semi-finalists for the 17-year period before and after the change. In all cases the distribution for the 2001-17 period lies above the distribution for the 1984-2000 period. This suggests less competitive balance.
It is possible to condense the distribution into a single number. One such measure is the HHI measure of market concentration and it is calculated as the sum of each participant's market share squared. The HHI for 1984-2000 is 1,834 and it increases to 2,180 for the period 2001-2017. A larger HHI suggests less competitive balance, e.g. if one team won all 17 titles then it would increase to a maximum of 10,000.
It is possible to repeat the pictorial presentation, and the concentration ratio calculations, for wider "market definitions". Figure 2 presents the distribution for finalists and Figure 3 for semi-finalists. The HHI measures for finalists are 1,263 (1984-2000) and 1,644 (2001-2017). The numbers for the semi-finalists are 839 (1984-2000) and 1,263 (2001-2017). The pictures and index numbers suggest increased concentration and less competitive balance.
All of the evidence points in the direction of less competitive balance since 2001. Next year marks another significant change in competition structure. I expect this change will also favour the stronger teams.