I understand that the Hitechnic Gyro was made for NXT but are there any advantages of using it over the normal lego gyro in EV3??
IMO there are no advantages of the old Hitech gyro: The most fundamental difference is that the Hitechnic Gyro is a analog (ADC) device while the EV3 Gyro is digital (serial). This makes the Hitechnic Gyro badly suffer from drift and oscillating offsets (both at stand still and by changing output voltages caused by electricity consumers such as motors switched on/off) which has to be filtered off. Digital sensors like the new Lego gyro are not affected by these interferences - basically - at all.