ConVersion Rates

[Taqwus]

For most nations, it's 200 gold a pop. That might be more useful in other ways, especially if you're not sure you can hold the province for that long. Depends on whether or not you're gold-starved.
With some setups, it might be worth NOT spreading your dominion everywhere, creating a weak/no-dominion zone with Stone Idols plus not building temples. You might do this if you want to locally escape negative aspects of your dominion, e.g. the mass death from AE/SG Ermor or CW Pangaea, or drain scale so your non-Master Smith researchers can get something done, or keeping your Miasma away from your Library and Sages.