AIR-SAP2602E---胖
AIR-CAP2602I----瘦
"SAP" means stand-alone AP. In the "old tongue", it means autonomous IOS (aIOS). CAP means it's controller-based IOS or LWAP/CAPWAP
http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps12534/data_sheet_c78-709514.html