You can't get much more subjective than that, but his point is well taken. And if you are working in a reverberant church building, you are already rather limited in what kinds of effects you can add, and how much as well. For instance, if the acoustics of the sanctuary provides a strong reverb sound with a reverb time of 3 seconds, you probably have absolutely no need to add any artificial reverb to the vocals. To do so could totally wipe out any chance for intelligibility of those vocals in that room. There is a slight chance in this setting, however, that an engineer mixing the same group of singers and players for the video tape or audio cassette may indeed need the aid of an artificial reverb unit to better blend the vocals.
Digital delays are another subject.
No one in the congregation will have any chance of understanding the words if you confuse them further with another delay. It seems so academic, yet I mention it because I have seen some engineers do this same type of thing - folks who should have known better. One final brief overview. Think through all of the routing possibilities. In a pinch, however, you can plug the output of a line level device into them.