Quote from BlueTronFTW »Okay, question: why is through the breach/scapeshift bad combos, but splinter twin is a good one? I mean, fundamentally I get why twin is good, but why are the two that are available entirely unacceptable.
Splinter Twin’s other half of its combo could be used to execute a tempo gameplan, slowing your opponent down while you tried to last to your combo (or just get them with Pestermite beats). Breach/Emrakul are basically useless unless you have both in hand.
Scapeshift needs to devote a lot of deckbuilding space to getting lands out, since the deck wins by comboing with the lands you have in play. Twin required little deckbuilding space for the actual combo, allowing it to use that space for cards that helped dig for the combo, or helped it survive until the combo could be executed.
…but, Twin was banned. It was too good to NOT run in that color combination.