All thermostatic valves are pressure balanced, but not all pressure balanced valves are thermostatic. Pressure balancing tries to maintain the original proportions of hot and cold water by balancing any pressure fluctuations. Thermostatic maintains temperature by controlling the mix of hot and cold water. Your system does not suggest either one as a preferred choice. It depends on what your desires are as far as a stable water temperature, balanced against the much higher cost of a thermostatic valve plus the fact that not all have an on/off function so you have to add a volume control valve to them.