The listings show ratings from 100,000 BTU/h up to 191,000 BTU/h. The labeled tank capacities shown are 4.3 Gal and 8 Gal.

Both units advertise precise temperature control. One model features an LED display with a touch panel on the heater; the other provides a wired control panel for remote adjustment.

Listed protections include leakage protection, flameout protection, dry-burn protection, overheating protection, timeout protection, pipe-damage protection, high-temperature lock, wind-pressure protection, and anti-freeze protection.

The indoor unit specifies a standard 1/2-inch NPT connector. The outdoor unit specifies a standard 3/4-inch NPT connector.

One unit includes an onboard LED touch display for local control. The other unit includes a 32.8 ft wired control panel and an external controller in the package for remote adjustment.

One listing shows overall dimensions of 21.65 × 6.3 × 13.78 inches and a weight of 19.75 pounds. The other listing shows dimensions of 24.8 × 6.89 × 15.75 inches and a weight of 38.8 pounds.

Yes — both product descriptions explicitly list “anti-freeze protection” among their safety protections.

Both units are specified as powered by propane.