How should I capture? DV, USB, or S-video?
Capturing via DV (aka I1994, ilink or Firewire) is a lossless process - the video transferred from your camcorder is an identical copy of the original. This is possible due to Firewire permitting fast data transfer rates - faster than the rates USB allows. If you capture via S-video (or indeed USB), you'll necesarily see a reduction in the quality of your captured video, so always opt for the DV option if available
A firewire connection also enables remote control of camcorder functions via the PC.
What capture card should I buy?
Remember that all Firewire cards are created equal. A bog standard firewire card is less than $25/£25 and combined with video capture software, will enable DV capture from your camcorder.