Some high level players use the extra 2 buttons for advanced tactics such as plinking. (you can do it with 6 buttons too, but you have more options for different button placement with 8)
33 times out of 51, the Qanba activated on the same frame as the Cthulu. 14 times out of 51, the Cthulu activated a frame faster. 1 time, the Qanba activated a frame faster. While that test certainly shows that the Qanba runs a bit behind the Cthulu, that was only 33.33% of the time. Compared to the amount of work involved opening up and installing one of Toodles’s board, which is still the gold standard in dual modding, the Qanba measures up pretty well. In addition, the boards in the second batch of Qanbas were upgraded.
Having played on Qanbas myself while owning a Kitty-modded TE, I can tell you that the new Qanbas are very nice quality sticks, and the easiest way to get a dual-modded stick, especially if you don’t have someone to install a PS360 or Cthulu board in a TE.