Why convert the starting scout to a prophet in turn 1

[Gandalf Parker]

As with everything there are pros and cons.
For some nations the dominion in Dominions is very important. For some the priests are also so important as to want to squeeze every possible one out without sacrificing your few good war commanders.

The game settings can affect quite abit also. Small-map blitz games means waiting for safe expansion or a better prophet can be a very bad idea when compared to putting a stealth preacher up next to your neighbor very early in the game.

Ive also seen the tactic of using the stealth-preaching immediately to push your dominion a certain direction in order to prepare an area for the arrival of their god (a Super Combat pretender). Not only a good tactic but also a very thematic role play.