It depends on the humidity.

During seasons when humidity is low, I use the Zoomed Repti Rock water dish put half-way over the heater.

When humidity is high, I use the Exo-terra Water Dish.

I found that even when the Exo-terra water dish is on top of the heater, it doesn't raise the humidity by much. And I also found that the Zoomed Repti Rock raises the humidity even if it's not on the heater.

I only have 4 snakes and they're all on display vivariums. Or was. One of them is currently maternally incubating in a sterilite bin.