One of the problems of explaining the differences between tubing types is that all things are not equal. Reynolds 531 was made with different tubing wall thicknesses from very thin to thick (22/25 to 19/22 wire gauge). It is the thickness and diameter of the tube that effects stiffness and not the alloy being used. Also tubing is made with different butting profiles (longer and shorter lengths) and where a builder chooses to miter the tubes within the butting profile might make a little difference too. This is why it is a meaningless explanation to say one bike with 531 rides differently than one with 853. They may will ride differently but the reason has to do with wall thickness and tubing diameter and not the alloy the tubes were made with.