I switched from my 18MZ to the DS-24 this spring. I would never go back. Just FYI I just setup my Avanti XXL and I used 11 functions for basic stuff plus smoke and gyro. My BVM F-16 with uses 17. If you needed stuff like lights, canopy, speedbrake, AB LED, airspeed calls, etc you could easily run out of functions on the DS-16. IMO Danny is correct, go for the 24.
Gary