"Hey Hol, did you know that both 'indexes' and 'indices' are correct?"
"Uh, yes. Actually, I think I did know that."
"Well, don't you think that's kind of unfair?"
"Unfair? What do you mean, unfair?"
"Well, say you use 'indices' in conversation. Then people know that you know a little something, right?"
"But if you can say 'indexes' as well, and it's still correct, then that seems like sort of a cop-out. No-one's going to be impressed with 'indices' anymore. They're not going to think that you know a little something. They're just going to think you're the kind of tool who says things like 'indices' when 'indexes' will do just as well."
"Oh my god, you're so right."
"Actually, though, I still think you can get away with 'indices' and sound clever. I mean, most people who would have said 'indexes' are going to feel stupid when you bust out the 'indices,' aren't they? They'll probably think they've been saying 'indexes' wrong all those years and feel awful about it. I think you can still have the upper hand."
"Yeah, true. Hey, do I come off the freeway here?"
"Nope, next exit. So listen, how do you feel about 'criteria' versus 'criterium'?"