The GPIB-USB-B supports both NI-488.2 and NI-VISA APIs. The Agilent 82357A only supports the VISA API. National Instruments has done quite a bit of work to ensure that the GPIB-USB-B driver maintains backwards compatibility with previous NI-488.2 interface drivers. We have also done extensive testing with LabVIEW. With the GPIB-USB-B, you'll have the luxury of selecting from a wide range of programming environments and APIs.
Craig A.
National Instruments Engineer