RHPs biggest advantage is a vertical gradient. They make a perfect gradient up and down. norwegn113 has demonstrated a basic failing of RHPs and where all the confusion comes from. In a relatively small space ambient air temps ranging from 78 to 86? unlikely. Air will move by thermal currents. Clearly 8ºF air temp difference is not very likely in a 4-5 sq. foot open space. Measuring ambient temps is complicated under RHPs, they need to be shielded. This leads people to believe RHPs heat air.

Stop and think on it, is the air going to be 8ºF inside an enclosure from one side to the other? Very unlikely. The RHP heats the warm side probe and does not reflect the true air temps.

RHPs work fine they need a fair bit of space and the oldest manufacturer makes a guards for their products. They heat objects so do UTHs the change in ambient temps are about the same. There is no point to have both they do the same thing. I am have had this debate here before but do your own math.

Lets use RB pricing so same thermostat for both lets just say you need 3 feet of 4" heat tape so 3x $2.10 so $6.30 and 4$ for the wire set 10.30 total. That uses max 18 watts.

The RB RHP is $ 64.99 at lets go with the lowest wattage 28w.

UTH usually are set basically to the desired surface temps. (give or take a degree or two.) Typically a RHP surface is greater than 25ºF than the set point.

My math says more power higher purchase price is more expensive.

I would suggest that a RHP can be used for arboreal enclosures and terrestrial enclosures that cannot be heated thorough the floor.

I would suggest a proportional thermostat for RHP UTH it is more debatable IMO. There is no buffer with RHP, they heat quickly so when on there is a marked increase in temps and when off the same. Proportional holds the same temp basically all the time. No big swings.

To me, for terrestrial enclosures, it is an option when UTHs will not work well.