Everything I've read in reviews says that Ultegra is an upgrade due to weight savings and construction materials, but the technology is basically the same. When I was upgrading my bike I was going to go with 105, but found Ultegra front and rear deraileurs (on line) for almost the same price as 105. The shifters were almost $100 dollar difference though, so I went with 105 shifters. Everything woks together great.