the difference between the two is the regulatory domain they work on. The 802.11 specification as regulatory domains defines the different parameters for antenna gain, transmit power, channel selection, and so on.
A (A regulatory domain - FCC):North America, South America, Central America, Australia, New Zealand, various parts of Asia
E (E regulatory domain - ETSI):Europe, Middle East, Africa, various parts of Asia
As you can see in this link European sites sell the European product: Cisco AIR-CAP2602I-E-K9
Find all regions divided by Cisco here: http://www.cisco.com/c/en/us/products/collateral/wireless/access-points/product_data_sheet0900aecd80537b6a.html