Need to replace a gas hot water heater with direct venting. Currently have a 15 year old 75 gallon unit. 4 in family (three baths). Never take more than 2 showers at a time or within an hour (unless we have guests). But have growing kids. My plumber uses AO Smith. He suggested a 75 gallon replacement. I started to look into more efficient units and identified two: XGV-50 and the vertex (highly efficient) models.

The XGV-50 has 88 gallon first hour delivery but recovery of only 41 gallons. It has 40,000BTU input/hour and Energy factor of .62.

The Vertex model (GPHE-50) has 127 gallon first hour delivery, 92 gallon recovery but uses 76,000BTU input.

The 75 gallon unit doesn't have a first hour delivery rating, recovers 81 gallons and uses 75,100BTU (model PCG75 or FCG75).

I have no idea how best to make a decision. I want to be conscientious about energy usage but dont want to be in a situation where I'll regret having to take cold showers. Any thoughts or experience with these (or other) models?