I never said it was better. I just said they are not the same in size. I am a firm believer that the welding wire is just as good when it comes to power transfer as actuall amp install wire. You just need to usually get one size bigger in welding wire. Now, Streetwires and most of the others are the same size as 1/0ga welding wire. It's just the few like Knu Kollossus, Kicker Hyperflex and Lighting Audio that are larger in size.
The only real benefit amp wire has over welding wire is that amp wire is usually tinned and will not corrode as easily, much like marine grade wire. The jacket on welding wire is water and oil resistant as well.
You should still be able to get 2/0ga welding wire from that source cheaper than Knu's Kollossus and much cheaper than Kicker Hyperflex and Lighting Audio.
It's the cover on the Kicker wire that makes it so flexible. I think that cover does not offer enough protection against scrapes and cuts like the other manufactures covers (Kickers Hyperflex cover is way to soft). Maybe I just worry too much about stuff like that but it offers me piece of mind.
I knew about your source over two years ago when he was selling 1/0ga wire for $00.89 per ft.
Look below for a comparison of the wire.
The orange wire in the middle is the 1/0ga wire you will receive (maybe a different color but this was from that link you posted). The ***** black wire to the right of it is 1/0ga Lighting Audio and the red wire to the left of it is 2/0ga welding wire from the same place. As you can see, the Lighting Audio wire is larger than the 1/0ga welding wire and basically the same size as the 2/0ga welding wire.
No, I don't think the actual amp wire is worth 4X the amount of welding wire.