The 105 stuff works well and it all works together. I have even used a Tiagra RD and it works at least as well as the Ultegra. That extra weight comes from extra material and stiffer, heavier material. In some cases this lends more stiffness to the unit. The added stiffness, especially in the FD, can help shifting under load.

The weight weenie in me usually goes for the lighter component, but the others really work well. I do use a 105 Triple FD on our primary tandem. Steel is stiff and it works great. Before anyone screams Frankenbike, the pros often have substituted lower ranked components when they work better. SRAM's Force FD is often used instead of the Red because of Red's lack of stiffness. Of course the pros must stay with the sponsor's brand.

Wayne