One example: What can legacy text do better or more than title & text? Except of course - if you have used legacy text in previous projects and want to open it again. Or would that just be displayed with title & text?
"What can legacy text do better or more than title & text?"
There's no bug in Legacy Text which replaces some fonts thus makes Titles & Text unusuable for some of us users. Also, there is no shearing, no line compressing, no kerning modification in Titles & Text.
So I seldom use Titles & Text and prefer both Legacy Text and ProType Titler most of the time.
Opening and editing previous projects with deprecated features is no problem. Only adding deprecated features to new projects is not possible when they're not enabled in the deprecated features tab. When you don't need them, you can leave them disabled and you're still able to edit previous projects.