They all do the same thing when they work. Some chipsets have compatibility problems with non-XP OSes. But other than that, they're all good.
Extra features would be a firewire cable, cheesy video editing software, an internal FW port, or FW800/USB ports.
Look at newegg.com, pricewatch.com, resellerratings.com for new ones.
2- Some of the audigy sound cards have firewire... but I don't feel that good with a consumer sound card (I'd feel better with the m-audio revolution 7.1 if sound was important)
I have a Canopus ADVC-1394 Video Capture card with Firewire and compsite. There are some newer hardware card and boxes the Canopus produces too. I really like the Canopus products. My canopus card has captured freat for several years now.