Always go with the electrical. This way you have oil or water lines running into the car. I would recommend a high quality brand such as Greddy, HKS, or Apex'I as well! I have the Greddy gauges and they have saved my engine once already when the oil pressure dropped too low. Worth every penny.
Right after where the water enters the motor, right behind the thermostat, there is a line that branches off. Its a rubber hose, that sends water to the turbo. I cut the hose in half and put in a NOS brand inline fitting. Its normally used in fuel lines to tap a fuel pressure sending unit. Instead i put the temp sending unit, and voila, 180 degree readings on my gauge