The cnPilot E500, E501S and E502S are three Outdoor Wi-Fi Enterprise that are alike in several ways (2x2 802.11ac, PoE-out support, LTE Filter, IP67 rated) with the main difference being the type of integrated antenna within the unit:
E500 : Omnidirectional Antenna
E501S: 90-120 degree Sector Antenna
E502S: 30 degree Sector Antenna
So what are some of the use-cases of each?
The E500 is best suited for medium to low interference areas where the AP will be installed in a location that ideally needs wide coverage. This could be a pole for 360-degree or in some cases even off a wall for 180 degree coverage in front of the AP. Typical use-case is a network with low number of other APs in the vicinity such as Rural or Semi-Urban public WiFi, Parks, private property such as parking lots, hotel outdoors, marinas, industrial locations etc.
The E501S is best suited for medium to high interference areas such as semi-urban or urban Public Wi-Fi. The AP could be installed on poles or towers where there are other devices present, and the high gain Sector antenna will provide good shielding from interference sources behind the AP. The high gain antenna on the E501S is also ideal for providing long range coverage for applications such as a wireless mesh link between buildings in a campus.
The E502S with its narrow width, high gain sector antenna is ideal for very dense deployments such as stadiums and event-halls. A number of these APs would typically be installed with focussed coverage from each covering small sections of the total area. This way each AP can serve up large number of clients while avoiding problems of creating interference or dealing with interference from neighbors which an Omni antenna would undergo. The E502S can also be used for focussed WiFi coverage say along a road, or along the aisles in a warehouse. It is also ideal for long range wireless mesh link between buildings on a campus.
The two sector antenna APs (E501S and E502S) also have a tilting mechanism in their pole and wall mount brackets to allow better positioning of the AP for focussed coverage.
In summary, between the three APs they provide different coverage capabilities to ensure any outdoor enterprise Wi-Fi application is handled. They also run the same software features so while users can pick the right Access Point for each application, in some networks even a mix-and-match of the APs works.