They give you an accurate reading of how much ballast is actually in the bags. Timers do not do this by themselves, it's all a guesstimate based on the time it takes to pump the ballast. So, they're much more accurate now. They also automatically reset your fill and drain time every time the ballast is completely full or empty. For example, in the past you could fill the bags and be venting ballast at 80% full, now it will automatically reset the timer to 100% so you have the full drain time to drain them down. AND, the sensors will show you when enough air escapes the bags to be able to top them off again, essentially keeping you completely full at all times.