The GPIB Interface Guide
History of GPIB
Since the inception of serial and parallel connections, and eventually USB, GPIB connections have been mainly reserved for industrial and scientific instruments.
USB to GPIB: Perhaps the most common method of connecting a modern computer with a GPIB instrument, the USB to GPIB turns your USB port into a GPIB port. Since GPIB's transfer speed maxes out at a relatively low rate (8 Mb/s), you don't have to worry about the USB port being the bottleneck. GPIB will almost always be the bottleneck. USB, however, does have the problem of a length limitation. USB is only guaranteed to work over about 16 feet.
Ethernet to GPIB: This is a very convenient way to control GPIB instruments from a computer. The GPIB instrument is connected to the computer through the network. The main factor that makes this solution more convenient for GPIB instrument operators is the ability to control a GPIB device remotely, which USB does not offer.
GPIB PCI: For controlling GPIB instruments from a dedicated PC, a PCI card is probably the best option. With USB, the connection is usually a temporary one. This is a cost effective solution if your PC will stay permanently connected. Since GPIB's distance limitation is 20 meters (65.6 ft.), PCI is a good solution for semi-remote applications.