In a previous post I singled out Shimano for whipping some marketing on us while we attended their technical seminar at the Park Tech Summit, but to be fair, SRAM did some of their own pitching of product, and in some ways it was kind of bizarre.
Essentially, the guy at SRAM spent a good chunk of time espousing the advantages of the design of their rear derailleurs, and how they differ from Shimano's derailleurs. In short, the main things they highlighted were the following: a two-spring rather than three-spring system, a more dramatically slanted main parallelogram body, no side to side "float" in the upper pulley, and an upper pulley that is concentric with the pulley cage pivot point. Each of these features were explained as ways in which SRAM drivetrain designers maintain a consistent distance between the upper derailleur pulley and the rear sprockets, through the range of travel of the derailleur, and regardless of the position of the chain on the front chain rings.
It all sounds good, and their derailleurs do work well, but to anyone who has followed derailleur design for any length of time, there's something familiar here. Each of those features were central to the design of SunTour derailleurs, back in the 70s. SunTour was the "other" Japanese company, competing with Shimano for a chunk of the drivetrain component market. A good, concise history of SunTour appears here:
The short version is that SunTour won a few battles over the years, but ultimately lost the war. Shimano became the dominant force in drivetrains, in large part due to their successful introduction of a working, indexed shifting system in the mid-80s. And according to much of the cycling press at the time, and since, it was Shimano adapting SunTour's slant parallelogram design, along with incorporating their own three-spring mechanism, floating upper pulley, and doing away with the concentric upper pulley that made the system work so well. So it's more than a little strange to see the very same features that SunTour used now being touted as having advantages over Shimano's system. To their credit, the folks at SRAM did point out that there were pros and cons to each design, but it's clear which they believe is the better system.
So who's right? Which is better? Honestly, they both work really well. I've worked on and ridden a lot of bikes with both Shimano and SRAM derailleurs and shifters (and lots of old SunTour stuff too), and they all work just fine. As with so many things in the industry, the similarities outweigh the differences in my opinion. It is fascinating though to see how "everything old is new again"... so many of today's "innovations" have been around a lot longer than the makers want you to know.
(On a side note, I'm not forgetting the other giant of the component world, Campagnolo. They are still a dominant force in the road bike market, of course. But I opted to skip their seminar, as we rarely see any of their components come into our shop, since we aren't really a "roadie" shop.)