That's how progress in technology works ;-)
However, there are a couple of areas where the AP-325 is superior to AP-515:
- AP-325 has a 4x4 radio in the 2.4GHz band, while AP-515 only supports 2x2 MIMO
- AP-325 supports POE on both Ethernet ports (redundancy), whereas AP-515 only supports that on E0
- Power consumption is a bit lower on AP-325