I have installed more than 200 E400s, and 50 E500Ss, i always find E400 performing better than E500 in terms of distance(coverage), but E500 have disappointed me in several occasions. The placement of antennas needs to be checked. is E500 true omni? what is the gain? maximum coverage in metres?
I'm not sure why you're receiving better range on the E400. Is the transmit power is set at a lower level on the E500? How about the client devices, are the client devices connecting to the E400 the same as the devices connecting to the E500?