I need to create some concrete document regarding the replication method.
We want to suggest best method for load balancing to client.
If you're wanting load balancing, then you need a hot standby and pgPool-II. This will send writes to the master and reads to the slave.
You probably want async replication. Unless you're doing financial transaction (or similar) where it must be guaranteed to be written in two places (then you want sync). Note though that this both slows down the master's performance (it waits for the slave to ACK the write) and makes the slave a point of failure since the master can't commit if it is down (unless you setup multiple slaves and have them all ready to assume the sync role)