Have there been any studies on which fly-by-wire pilot interface is preferred; rate control or direct control? Provided an aircraft with a fly-by-wire system, there are basically two possible choices when it comes deciding how to let the pilots interface with it:


rate control / attitude hold: a deflection of the stick will command a certain rate, releasing it will make the system maintain the current attitude. See the Airbus Normal control law.
direct control: a deflection of the yoke will directly translate to a deflection of the surfaces, mimicking the "old" mechanical control setup. It is my understanding that this is the design choice of Boeing in its new aircrafts.


I do not wish to discuss how Airbus and Boeing made their design decisions, but rather see if there has been performed a study on what interface is preferred by pilots, eventually differentiating among private/commercial pilots or Airbus/Boeing certified pilots or even pure civil/(former) military pilots.

Does any of you have any reference?
I have no study to refer to, but I expect the results to differ very much from group to group. 

For airline operations, I imagine the objective of the pilot is often to maintain a constant attitude, varied with a smooth transition to another attitude. This would be easy to achieve with the first option you describe. 

For military operations, I think a rapid feedback is desired. This aligns better with the seconds option you describe. 

When you would perform a study under pilots, the response you'll get will very likely be that they prefer whatever they are used to at the moment.