Repeater

Advantage:

• This mode is used to conveniently and quickly repeat a remote weak
  wireless signal in a couple of steps for internet access. You will only
  need to know the security encryption used in the source wifi/router. On
  the ERB series, you can perform repeating by pressing on the WPS button
  with a corresponding source wifi/router with the WPS function too.
• Can repeat a wireless signal of any other brand given that you have the
  correct wireless security credentials

Disadvantage:

• There is no network transparency and some other network elements such as
  servers, NAS, printers may not appear properly. Repeater mode is only
  good for internet browsing, email, etc.
• In some source Wi-Fi (i.e. public hotspots) where user authentication is
  required the login or splash page may not appear for you to log in as
  most authentication requires to capture the MAC address of your computer
  which may not successfully pass through the repeater.

  
  WDS AP

Advantage:

• This mode is used to create a transparent wireless repeating network
  where the connecting devices's MAC Address can successfully pass
  through the network and access to other network elements such as
  printers, NAS, server.

Disadvantage:

• The MAC addresses of corresponding access points must be added to each
  other before the WDS can work. For example, you must add first AP's
  MAC into the second AP and also the second AP's mac address into
  the first AP.
• WDS works within the same brand and preferably within the same models.
  Though some people have claimed success with different models or brands,
  only the same model is guaranteed by EnGenius. 

Product Note:
The EAP, ECB, ERA and ERB series
model have universal repeater & WDS mode whereas
ESR series model have only WDS mode.

Note: In both repeater or WDS mode, the total capable bandwidth of
the access point is halved. The same wireless channel & security
encryption must be used in all repeating and WDS mode.