http://www.channelfireball.com/articles/the-top-5-legacy-decks/

This list is from RG Lands expert and GP SeaTac winner Jarvis Yu.

A number of people have switched over to playing Dark Lands, a lands variant that is playing black for cards like Thoughtseize, Abrupt Decay, and Dark Confidant in the 75. I believe that version is simply worse than regular old RG Lands.

Lands has a weak Miracles matchup, but a strong matchup against most of the rest of the field. There are a lot of decks that are dead to a 20/20 Marit Lage, which is capable of coming down as early as turn 2 with the right draw. There are a lot of other decks that can’t beat the grindy inevitability of Life from the Loam, Punishing Fire, and effects like Wasteland and Rishadan Port to attack your mana.

One other huge factor that makes Lands great is that it gets a lot of free wins. There are a lot of decks out there that have atrocious Lands matchups, and it’s hard to overstate the value of free wins every now and again. Some of the other top decks like Miracles or Grixis Delver don’t get free wins, and missing out on that is a real loss.