I responded to the same post in the BRZ side so just pasting the response here as well.
The GR86 is not available yet. The earliest you will find one to test drive is probably January.
To answer your question, it is best to explain to you about the difference between the two.
Steering response:
The two cars should have the same steering tune. That sharp steering people feels is probably due to the difference in suspension tuning which directly affect the body movement of the car when cornering. Because the GR86 is more tail happy with its suspension tuning, this is likely what causes the steering feel of the GR86 to be better than the BRZ.
Throttle response:
Also comes down to the tune of the throttle body. The BRZ tuning is more linear so whatever amount of throttle input you give, that is how much the throttle body will open. The GR86 tune makes the throttle body open sooner so you don't have to floor it to get the max output. But in terms of performance, the two cars will be similar as the powertrain is the same.
Brake response:
I don't think there is a difference in terms of brake response for both cars because the components used to build the brake itself should be the same. The difference people experience is also likely from the body movement, which is caused by the different suspension tuning. The GR86 has a lower front suspension rate compare to the BRZ so during hard braking situation, it is likely the GR86 will dip more in the front which makes you feel like you are braking harder in the GR86, but in fact that is just the difference in body movement.
Overall, if you are looking for a more aggressive feel, GR86 will be better for you. But if you want a more stable feel, BRZ is the one to go.
