To bad I didn't come across Ciara Stewart's blog earlier. (Thanks to a link at Marta's Vamp Wire blog) I came across Ciara's post link to author Keri Arthur's definition of both subgenres in a pretty straight forward fashion. (The full article is pretty informative also).
Usually written in the 3rd person. Main characters are Hero and Heroine and they MUST have a happily ever after together. This couple is exclusive. Love shall overcome is the theme. Each book in the series has a new hero/heroine pair, and these characters often show up as secondary characters in the other books in the series.
Examples: JR Ward’s Black Dagger Brotherhood (perhaps not now), Nalini Singh’s Psy/Changelings series, Kresley Cole’s Immortals After Dark series, Marjorie M. Liu’s Dirk & Steele series, Meljean Brooks’ Guardian series, Lori Handeland’s Nightcreature series , Lara Adrian’s Midnight Breeds series, Sherrilyn Kenyon’s Dark Hunter series, Alexis Morgan’s Paladins of Darkness series,
Usually written in the first person. Theme is horror, not love. A single protagonist often narrates the entire series. (Kelly Armstrong’s Women of the Otherworld is a notable exception). The protagonist is often a cynical, fiercely independent, tough chick with commitment and trust issues. lol. (Jim Butcher’s Harry Dresden is a notable exception.) There may be a love interest, but it is subtle and may build over the course of the series. Or maybe the more the merrier, a la Anita Blake.
Examples: Laurell K Hamilton’s Antia Blake series, Ilona Andrews’ Kate Daniels’s series, Patricia Briggs’ Mercy Thompson series, Kelly Armstrong’s Women of the Otherworld series, Kim Harrison’s Rachel Morgan series, Jim Butcher’s Harry Dresden series, Marjorie M. Liu’s Maxine Kiss series, Keri Arthur’s Riley Jensen series, Karen Chance’s Cassandra Palmer series, Jeanine Frost’s Night Huntress series
And there we go. :-)