The main advantage of the HE500 over the Ananda is twofold:
1) to my ears the driver is clearly superior. There wasn’t anything I heard the Ananda do that I wouldn’t say the HE500 could do better and differently.
2) its modability. Any pad that will fit the TH600, Beyerdynamic DT-series or Mr. Speaker EF will fit the HE500, plus with the fuzzor mod, bluetac mod and screen removal (all before cable swaps), one could tune an HE500 to sound similar to the Ananda or enhance its original voicing.
@bagwell359 has an HE500 with (if I remember correctly) the Fuzzor mod, new cables, screen removal and EF pads, his set probably sounds equal to yet drastically different from mine. There aren’t many if any mods available for the Ananda and no pad swaps short of DIY; with the right sets of reversible mods the HE500 is just consistently better.
Without a doubt HE500 drivers in the HE560 body with 2.5mm or 3.5mm connectors is a vastly superior headphone because it solves the comfort and ergo problems while maintaining the superior drivers. There are a number of these exact modded HE500’s on head-fi and I’m always tempted to buy one when they come up for sale. If you have the power or are willing to get it I would recommend the HE500 as the headphone to get over the Ananda, provided your willing to buy used and can handle the risk that entails.