Proper form for seated cable row?

Doberdawn

Okay. I've read books. I've watched videos. I have become frustrated trying to figure out what is the proper form.

For example, this guy only uses his arms and his back stays stationary:
http://www.youtube.com/watch?NR=1&v=GZbfZ033f74&feature=fvwp

But, this guy, pulls back with his back, leaving arms straight and then pulls back with his arms:
http://www.youtube.com/watch?v=-ykUDTcpuJE

This guy is the same but a little jerkier: http://www.youtube.com/watch?v=kMSajsZqniA

I've read you should pull arms in then use back. Keep arms stable and only use back/abs. Start with arms. Start with back. Pull in with arms as you come back up with back after having pulled back first with back.

I would love to hear which way YOU think is right and more importantly... WHY??? I'm trying to learn here and this is getting exasperating. LOL I'm an inquiring mind who wants to know.