Some say noticably stiffer, some say not, personally I've run both DA 7600's and Omniums, and thought the omniums were stiffer, not by a lot though, I'd imagine they're in the same ballpark as DA 7710. The biggest draw is the servicability and ease of use though, bb's are cheap, I've always had loads of problems with square taper cranks, at this price, I wouldn't think twice about going with them over DA or Campy.
Some say noticably stiffer, some say not, personally I've run both DA 7600's and Omniums, and thought the omniums were stiffer, not by a lot though, I'd imagine they're in the same ballpark as DA 7710. The biggest draw is the servicability and ease of use though, bb's are cheap, I've always had loads of problems with square taper cranks, at this price, I wouldn't think twice about going with them over DA or Campy.