Originally Posted by Maelochs

Test-ride both.

Red as I understand it is deemed to be on par with Dura-Ace---very light, top-quality stuff. Ultegra is supposed to be step below ... but some prefer Sram's double-tap to Shimano's double-levers.

I don't think you could go wrong with either.

If nothing else, consider buying the SL8 and selling the Sram Red if you don't like it ... you could likely get a full Ultegra group with a few bucks left over.