Hm, I don't think thats how it works, but i might be mistaken.
Itinerant preachers = +3 range. This means a majority city will pressure all cities within 13 tiles with standard pressure. this means more followers (probably only 1 or 2 per city at first) in farther away cities. Thats why I assume its better for things like tithe, which don't care where the 4 followers are.
Religious texts = +% but only within the original 10 tiles. Only majority cities generate this pressure, as well. therefore, religious texts results in a higher percentage of followers within cities that are within 10 tiles of the majority city. This leads to faster majorities, which helps beliefs like ceremonial burial, which only work for majority cities.
Is this incorrect?
This is correct, but to spread even further, of course, you have to make more cities have majority, and here Texts shine.
I had numerous occasions when even my own my cities would gain population faster then pressure would convert citizens and I'd had to stop growth to save on missionaries. Not to mention AI crazy growth speeds
I could be mistaken, but it seems that ~100 pressure is needed to convert 1 citizen, so ~16 turns with 6 pressure ~12 turns with 8 pressure. As you have to convert only half of growth to be in majority, that is ~8 turns and ~6 turns respectively.
With Texts you get new majorities sooner and... well, I can't put a mathematical model to it, but with Preachers I had my religion crumble to AI missionaries and with Texts it never did, pressure is too high and you recover fast