Eibach uses progressive rates in the rear while H&R uses linear. Both use linear rates on the front. I've noticed that Eibach lowers the rear more than H&R. I don't think you can get a definate answer as to which is stiffer as neither manufactur releases the spring rate data and you can't really compare the two by feel unless both cars have the same tires, shocks, etc. But I think the general census is that if you want something more comfortable go with Eibachs and H&R for more sport. You really can't go wrong with either one as both are excellent.