Snitch and even moreso rat out are commonly associated with the criminal underworld, at least in the US. In contrast tattle-tale is more associated with the US South.
Green's Dictionary of Slang has many references for snitch: it occurs in the UK from the 18th century, and in the early 20th century across the US including a 1911 book of Arkansas slang. But the dominant usage is in crime stories, from WM Raine in 1909: ‘Say, Jimmie, C’n you keep a secret?’ ‘Sure. Course I can.’ ‘Won’t ever snitch?’ Through Nicholas Pileggi's 1985 mafia classic Wiseguys: Even the hacks who [...] couldn’t be bribed would never snitch on the guys who did. and right up into the 21st century. The OED has snitch as a verb from 1801 in the UK, with various 20th century American references such as Arthur Miller (A View from the Bridge) and Budd Schulberg (What makes Sammy Run?), writers who attempted to represent life in American immigrant communities, so nothing very literary.
Green's has a host of references for rat out from 1975 in crime writer Edwin Torres, through a long list of famous American crime writers like Carl Hiaasen and Pileggi again. So it's very strongly associated with the criminal underworld. The OED doesn't have rat out. So it's a more recent criminal term.
Green's doesn't even have an entry for tattletale or tattle tale. The OED has a range of literary references from Mary Murfree (writing as CE Craddock) in 1889 - a wealthy Southern US writer known for tales of Appalachian life. There is also Faulkner and Carson McCullers, so it's reasonable to suggest an association with the Southern US.
