The Rheem Proterra PROPH50 T2 RH350 wins on efficiency metrics with a 3.75 UEF and 75-gallon first-hour rating per Rheem specs, beating the A.O. Smith Voltex PHPT 50's 3.45 UEF and 70 gallons. A.O. Smith remains competitive on price and noise levels according to owner feedback aggregated on Consumer Reports. Choose Rheem if energy savings over 10 years matter most; pick A.O. Smith for lower ini...