One is that you want to develop and make important all your POV characters -- even to the point of making sure you share an equivalent amount of time for each.
The other is to heavily weigh your POVs to make sure that the most important character got the bulk of them, with much fewer for the secondary POV, and still fewer for the tertiary one.
I will chirp, Depends on what sort of story you're writing.
Adding a POV character can lead to the question of why the story's events are deeply important to this character, and what he is looking for, and whether he gets it, and what he learns. And what he thinks of the main POV character. But you can also do minor characters who have a POV because they see something no major character does -- or, at least, no major character whose POV you can show, because the POV would reveal information that you want to keep secret yet. Indeed, if you never want to use the main character's POV, to allow him to keep his secrets, you could do it all with minor characters.
If POV characters reoccur, it's probably wise to start analyzing their characters. One-shots, however, just need to be adequately interesting, and not mislead the readers into thinking they will be significant later -- such as not including any information that the reader would expect to be significant later. Even if you detail a character so that the dead will not all be anonymous blanks, you don't want to mention a character's children in such a manner that we wonder why they don't get mentioned later.
And a work can have both types of secondary POVs, but the trick is to set it up up front. If every POV character becomes a deeply significant character with his own subplot, until chapter 7, the reader is going to wonder what the bit character will do later on. And if every secondary POV is a bit character, having the POV character from chapter 7 is also going to annoy.