The System Sensor 5351RB is indeed a notable upgrade from the 5251RB model. One of the key improvements is its enhanced sensitivity and detection capabilities, which ensure quicker and more accurate detection of smoke and fire hazards. Additionally, the 5351RB features advanced communication protocols, allowing for seamless integration with modern fire alarm systems and improved compatibility with newer technologies. Overall, users can expect improved performance and reliability with the 5351RB compared to its predecessor.