Simulate... let's say 10000 units of delay. Ignore haste and DW, they're a constant multiplier so they'll affect both equally here.
Kannagi/Sekka has a total 411 delay, Kannagi/Enchu has 452 delay. Let's only assume Brutal Earring for DA.
10000/411=24.3309002 rounds
10000/452=22.1238938 rounds
Add Brutal Earring and Enchu DA.
24.3309002*1.05=25.5474452 hits/hand in this timeframe, so that many hits for Kannagi
22.1238938*1.15=25.4424779
A small advantage for /Sekka, but an advantage nonetheless. Adding more DA gives /Sekka a further advantage. For instance, add Atheling Mantle, Twilight Belt, and /WAR:
24.3309002*1.2=29.1970802
22.1238938*1.3=28.7610619
See how the difference has increased?
Now, there's a further consideration:
This graph depicts speed of TP gain per unit time for various delays. Notice how TP gain begins to increase dramatically below 180 delay/hand. Now, DW is factored into TP gain, and NIN obviously has a lot of DW. Not only is the /Sekka setup swinging faster, it's going to gain TP at an increased rate as well. Factor in the fact that some of DW Enchu's TP gain will be overflow (exceed 100 TP within a given attack round) and the gap in WS frequency increases again.