I like both, but for different reasons. I like the hood feel of the Shimano, but I like double tap and the mechanical shift feel of SRAM. SRAM is quite a bit lighter than Shimano across the board., iirc, Rival is pretty close to the same weight as D/A. Force and Red are substantially lighter than D/A. so if weight matters SRAM is the way to go. for the record, a quick google search shows Force to be almost a full pound lighter than Ultegra for the complete group.

I currently ride SRAM, but I have no terrible objection to riding Shimano, I just like the double tap shifting and for me that makes sram worth it. in the end, like others have said, give it a try, ride 'em both and see which you prefer. if personal preference is a wash some of the 'on paper' measures could be a decider for you.