It's quicker because it is 20% bigger, not because it is one element verses two. With two elements, they are normally setup to operate with one or the other, not both. The hot water comes off of the top of the WH and the dip tube directs the incoming cold water towards the bottom of the tank. When you get close to running out of hot, the only element that normally is running is the one at the top which is trying to keep the water going out the pipe as hot as it can get it; otherwise, the bottom one kicks on once the top reaches the set point. So, with only one at the bottom, you might recover quicker, but the last of the water coming out might just end up getting colder and colder without that extra kick of the upper element. I'm told that you can get some where it can operate both elements at the same time, which would be larger than the single element one. Either might require rewiring and a new breaker, as the current draw is larger.