FPGA Memory Item vs FIFO Item

What is the difference between using a FPGA Memory Item () and a FPGA FIFO Item ()?

I am looking to offload data as quickly as possible between an FPGA target and a host VI application, however these two options seem to be used interchangably in the LabVIEW help documents and whitepapers.  I understand how DMA works from a Computer Science point of view, and would like to use this approach since it is the fastest (i need a very quick DAQ system).

Does anyone know what the specific difference between these are, and (more importantly), which will be faster for transfering U8 integer data?

They are both created by right clicking the FPGA Target:

Thanks in advance for any help! :)