Comrade said:
And I'm interested in understanding what I could miss with KT vs CA.
What specifically do you need your bike to do for you, and how do you want it to do them?
What specifically do you need your bike to be able to tell you (via display)?
If you make a list of these things, then we can help you figure out what system (or systems) are needed to do those things.
If you just want to know what the CAv3 can do, the Grin site and manual do a fair job of listing the major features. There are ways of combining various features to do specific jobs in specific ways that may not be listed, but there are so many possiblities I can't just make you a list.
Knowing what you want to do, with enough specific detail, we could tell you if that can be done with the CAv3 or not.
Essentially, the CAv3 takes in a number of sensor and control inputs, processes them thru whatever settings you've put into it for the various functions, and outputs a throttle signal to the controller based on all of those things. Since it's only output is a throttle signal, then it is directly compatible with any controller that has a throttle input (whether that is a PWM RC throttle or a variable-voltage throttle within the 0-5v range). To perform some functions, it may need other external hardware depending on what's already available on your bike.
The specific things it can take as inputs are listed in the Grin documentation, as are the specific settings available in the various menus.
The CA is NOT a display.
(just to make that absolutely clear to any readers now or in the future)
It is not designed in any way to communicate with any controller in any way other than sending it a throttle signal. It can only display the information that is monitored or created within the CAv3 itself, nothing that comes from a controller. It can't program anything outside of itself. If your controller requires programming, setup, or mode changes either initially or at the start of every power-on cycle, then you would still need whatever hardware is required for that by that specific controller.
(if that hardware is only needed for initial setup, then you don't have to mount it on the bike, but you still have to have it).