I have heard (but you'd have to verify with manufacturer) that the switch was due to a switch in mechanisms. They no longer could source the mechanism in the 508. I had a meridian tech tell me the 588 is unquestionably better than the 508, however there was a recent post here in which two members indicated that they had been told the opposite by someone at meridian. Unfortunately, unless you can find a dealer who still has a 508, it will be hard to demo them side by side. Price, btw, seems to be more related to what the market will bear than to manufacturing costs, so the expense may not be relevant to relative quality between the two.