Extract twang is a myth....Even Forrest at AHS has said so.
I discuss it here. http://www.homebrewtalk.com/f14/extract-twang-aging-129926/#post1463413
It's mostly somoeone tasting green beer and blaming it on something they heard about....rather than just realizing they tasted it too soon.
I prefer Dry to liquid extract. Just be aware that as it hits stem it clumps, but for giggles once I added my entire 10 pounds of dme for a recipe into the kettle at once, and with a lot of elbow grease it dissolved fine..but it took a lot of stirring....but it all dissolved.
When I am formulating any extract with grain recipes I ALWAYS base it around Extralight DME, then I get all my flavor and color complexity from my steeping (or partial mashing) grains. That way you get to use more and varied grains.
For example, let's say you are making an amber ale....If you based it around amber extract, you have very little room to get complexity from roasted or crystalized grains.....you run the risk of muddying the flavor and ending up too dark for your recipe.....
Staying with my Amber example...The Srm range for that style is SRM: 10 – 17 so if your base extract already puts you into 14 srms, you son't have much room to move around it....you may be able to sneak in a pound of crystal 30 let's say in it.
But if your Extralight DME has a color of 5 SRMs, you can really get into the recipe and play around with different combinations of grains until you get into the right color and Og range for the style.
It's kind of like making model airplanes....remember the "snap together" types that you started out with? You had maybe 8 pieces; 2 body halves two front wings, 2 rear wings and maybe 2 pieces for a cockpit, or two pieces for landing gear...
But if you got one of those 500 piece b52 bomber kits....you had a much more complex final product.