Neither. Patterns of Interference was not a "finish" to the series, as I hoped to do more, but it doesn't end in a cliffhanger and it does resolve some of the major threads from the previous books. There were longer-term character and story arcs that I'd hoped to develop in further books, so not everything gets resolved, but enough does that it works as a satisfactory stopping point.
After all, I usually got the ROTF contracts one at a time, with the exception of books 3 & 4, which were contracted together so I knew going in that I could make them a 2-parter. And I think I already had that contract while I was writing book 2, so I was able to end it with a tease for the next book. But when I was contracted for book 5, I didn't know whether I'd get to do any more, and I did want it to be a climax to some of the main story threads.
Just in general, I've been frustrated in the past by novel trilogies whose installments just abruptly stopped at what felt like arbitrary points and left me dangling for a year or two before the next installment, so it's always been my policy that if I write a trilogy or series, I structure it so that it naturally breaks down into distinct parts so that each installment tells a complete phase of the story from beginning to end and has a satisfactory resolution, rather than just feeling like a fragment of a story.