Which is best Rheem whole-home tankless water heater – GreenBuildingAdvisor

I would greatly appreciate experience and opinions on which of Rheem’s 27KW electric tankless heaters if the best choice for performance and durability:

A. Rheem Professional Classic RTEX-27

B. Richmond Essential RMTEX-27

C. Eemax HomeAdvantage II HA027240

D. ECOsmart ECO 27

E. Rheem Performance RETEX-27

A-D Have UAE “up to .94” and 3.5 GPM rating

E Has UAE “up to .93” and 2.7 GPM rating

The data is all from the respective products’ websites. All have same Amps and 3 heating elements. The GPM rating for E seems so much lower, that I wonder if it’s a mistake on the Rheem website.

A, B, C, & E have the same dimensions (17x17x3.625). A, B, & E have the same “Shipping Weight”, D lists 14.7 as simply “Weight,” so it may be that the units’ weights are all the same. They all have metal shells and backplates.

D is 9.25x19x4.25 and 10.9 pounds 

A, B, C, & E all have “Copper” for “Heating Element” and “Heat Exchanger” and “Brass NPT fittings.”

D has “Copper Sheathed” for “Heating Element” and “Stainless Steel” for “Heat Exchanger.” It lists simple “3/4″ NPT” as the “Water Connections.” It has a polymer shell, which would explain the much lighter weight.

They all list a warranty of 5 year for leaks and 1 year for parts that is bound to the equipment, not the owner. ECOsmart also offers a “Limited Lifetime” warranty for the initial owner.

It appears to me that A, B, & C are probably the same unit, just sold to fill under different branding. E is an outlier within the same design, which I can’t explain. (See attached image)

The ECO 24 is a different animal that was a product line that Eemax originally introduced, and then Rheem bought Eemax. (See attached image)

There are significant price differences among and within the six products. Today and tomorrow, a seller on AliExpress is listing the ECO 24 $346.68, free shipping, and free returns within 15 days.

Thanks in advance for any experiences or opinions.