They would all work. Which one you buy depends on a few factors. The pci/pci express versions mount inside your pc. Oviously your pc would need a free pci or pci express slot. Pci express is fairly new so you would have to have a pc with that technology. If your pc is very old, then you would have to buy an ISA slot version. With the usb version, you can use it with either a laptop or a regular pc. No need to open the case to use it - just plug it in. If you don't have a free slot or might need to move it occasionaly, go with this type. The enet version would be used if your pc was a long distance from the instruments. You are limited to a total cable length of 20 meters with gpib. With the enet type, you can plug it in anywhere you have a network drop.
Unless you are going to be developing a lot of instrument drivers from scratch or creating a gpib interface in a new instrument, you can skip the controllers with a "+" in the name. You probably would never use the builtin bus analyzer capability of those.
You can contact your local NI Sales Engineer or click on the 'Call Me Now' links that are on any of the product pages to speak directly with someone from NI.
