When writing a reveal about a character's past, is it better to make them talk about it or to use a flashback?

Flashbacks were seen as poor writing or something that might cause editing problems because of verb tense use and the potential for readers to lose track of what is happening. They are used to cover jumps in time. But a “wait a minute, what's going on here” by a reader is a distraction flaw where the reader is pulled out of the story to look at mechanics. They are used. But use them in a limited fashion. If you can do it through dialog, it's less distracting and more warm and chummy.