red vs ultegra isn't really a comparison I would make. red vs dura ace or force vs ultegra, rival vs 105 etc....
in regards to sram shifting vs shimano shifting is is extremely preference based. I love doubletap compared to having 2 levers. I rode 105 for a while and moving to sram felt crisper and more "clicky". I do have big hands so I prefer shimano's slightly larger hoods but I like srams shifting even more than that. If only I could have doubletap built into a more shimano style hood. As far as hoods go, campy takes the cake however.
to answer the original question, imo, red is better. lighter by a lot (250 grams is hard to find on a bike) and quicker shifting (zero loss on the front and rear) make it better in my book. but again, i wouldn't compare the two.