There is a very big difference between a modern ZF 7/8speed autobox or dual clutch automatic and a late 80's autobox. Todays auto's are far more intutive, with seamless instant changes that actually make the cars quicker, feel far more directrly connected to the wheels and usually come with Paddle shifters for more manual control.
The Z autobox is a lot slower to change gear, doesnt always pick the right gear at the right time, suffers with a lot of torque convertor slip and is a lot weaker/less reliable than its manual counterpart.
Besides that, the Auto equipped Z32 makes less power due to Turbo and exhaust camshaft differences in an attempt to claw back some response. It then transfers less of that power to the ground due to the lower transmission efficiency.