You imay find the hoods of one fits your hands better than the other. The sound issues with Red eminate from the cassette. I ride Force and it's just as quiet as Ultegra. I suspect if you swap out the cassette you probably lose most of the weight savings with Red though. The only real advantage I found with Ultegra is shifting from the small ring to the big ring was better.

I have ultegra 6700 drive line (RD, chain, cassette) with 105 5700 shifters and FD. I love it and is very precise and the shifting is positive and reassuring. The redesigned FD cage is so awesome and lets me have all gears available in either chainring. The ultegra 6700 STIs though (tested on a specialized tarmac) are so light (in feel), they'll make you wonder if you even pressed enough. Lol. With my current setup, I power up hills with no hiccups or problems. Either way, you're getting a great groupset. I like shimano, always have and like the fact so much of the Shimano stuff is common and interchangeable. Shimanos down fall has always been weight. Wish they'd get as light as SRAM. Then it'd be a no brainer.

My SuperSix came with Shimano 6700 shifted nice, I did not like the feel of the hoods though. I upgraded to Sram Red and Love it! I would not go back to Shimano -- Sram RED

you really can't go wrong with SRAM. It's simpler, easy to use and it works great. Plus it's cooler to say than SheManOh