You can use thinner copper and make longer extensions, because active cabling help compensate for attenuation and crosstalk. Really you can put any kind of DSP you want in there: skew, equalization, etc. DisplayPort is only spec'd for 3 meters over a passive cable, but goes up to 33 meters over an active cable. Also, although I can't remember a source, the Thunderbolt over copper uses about 25% of the power compared to the original optical version.