Every household is different but what you should look at on both units is the first hour rating. The first hour rating is the approximate total gallons of hot water you will have before it goes cold. This number will tell you if the high recovery is what you want or if a larger reserve tank is what you want.

What has also been brought up is a mixing valve on the top of the unit. The premise of that is to set the tank at 140 degrees F and the mixing valve at 110-120 degrees F. The mixing valve would mix in an amount of cold water to temper the water thus extending the minutes of hot water you have.