OW took the words out of my mouth
And I want to add on licker's observation.
SCs do not contradict G3. You can take a 4S or pathless Wyrm and make it a fine SC with or w/o G3.
SCs have their uses but IMHO they are mostly orthogonal to the G3 vs. D3 decision.
I still think G3 is better when you have a long term plan on a big map. In case you have a death dom nation or playing a small map or planning for a strong rush that won't end until complete victory then by all means take D3. Just don't be too surprised you won't be to most popular guy on the block b/c if you have death dominion and if you are rushing and leading the score graphs (which is your ideal with D3) you will be hard pressed to find friends.
OtoH a G3 peaceful nation would have that much more income and research that could jump it much faster to endgame research.
So when you make the G/D choice you better have a well thought of game plan
