Kathy
We have the XT in our rig. Still going strong. The water is heated MUCH higher than a standard water heater and a mixing valve on the backside mixes cold water with the hot water. Supposed to give you hot water longer than a standard. Only other difference other than price is that mixing valve. It will occasionally stick with minerals and such giving you very hot water.
If your the type that likes to take long hot showers go for the XT, otherwise the standard hot water heater will do just fine.
Hope this helps.
