From the Real-Time FIFO FAQ:
What is the difference between RT FIFOs and Queues?
Functionally, RT FIFOs and LabVIEW Queues are both First-in, First-out buffers. However, the following are the major differences between them:
Does that answer your question? The RT FIFOs are particularly good for moving data between loops deterministically (say from a data-acquisition loop at high speed to a non-deterministic loop that processes it). If you're using your queue like a global variable to store a single element then there's less of an advantage to the RT FIFO.
Great thanks for this, I'll digest the FAQ today and decide which is best for my application.