Is the Spark 2-axis gimbal "shakier" than the 3-axis gimbal of the Mavic's and Phantom's?
By not having a 3rd-axis (the pan direction), what penalty does the user take on when it comes to video quality?
Is it shakier or does it just not rotate in the pan direction while flying in a turn, for example??

The Spark comparison (http://www.dji.com/products/compare-consumer-drones) says it's gimabl is:  2 - Axis Mechanical Gimbal + UltraSmooth ..... what does "UltrSmooth" refer to ???
The Mavic comparison (http://www.dji.com/products/compare-consumer-drones) says it's gimbal is:  3-Axis Mechanical Gimbal

the sensor is the same...But in spark use a crop factor... so it can Stabilize the image ("UltrSmooth")

UltraSmooth is a new technology of DJI and it will reduce shake and rolling shutter effect, keeping shots stable and detailed.