I couldn't even BEGIN to compare the 2. I have only used the Qix on the Space Invaders/Qix machine, and my T-Stick plus is still sitting in a box of parts, having never actually been installed.
Between Qix and Ms. Pac, I say Ms. Pac.
Also, you can swap Happ Super handles into the Ms. Pac base, works perfectly, but it obviously has a longer throw from the longer handle. Good option if you want all your sticks to match. You MIGHT be able to order them from Happ that way if you asked.