My temps are good with RHPs alone. In winter, the cool ends are about 78 - 80, and basking temps are just where I want them. RHPs provide good basking heat from above, and they also heat the cage air which in my situation is a necessity. I've tried belly heat on few occasions, and while it did indeed give me a warm floor temp for the basking area it did next to nothing to raise the ambient temp in the cage, especially when using newspaper as a substrate. Just inches from the belly heat area I'd get temp readings not much higher than the outside room temperature.
I don't want a hot spot in a cold cage, and RHPs let me get the temps I need in year round, no matter which room I keep the cages. As I mentioned, I use proportional thermostats on some cages and they come in handy in the warmer weather.
With larger cages 4 feet and over, there is a bit of flexibility. I can use a 12 x 18" RHP, and during the winter months add a small 6 x 12" RHP in the cool end. In my 6-foot tegu cage I use an 18 x 24 RHP only, because I want a hot basking area of 110 and the 18 x 24 RHP throws a lot of heat.
As you know, getting the right basking and cool-end temps depends on room temperature, type and size of cage, type and location of the heating device, and requirements of the animal. For me, RHPs do the job.
Bill