This form of replication is appropriate for small data sets, infrequent
update periods (or for a one-time replication operation), or management simplicity.
Transactional replication can typically keep databases in sync within about five seconds of latency, depending on the underlying network infrastructure.
Merge replication allows data to be modified by the subscribers and synchronized at a later time. This synchronization could be as soon as a few seconds, or it could be a day later.
Immediate updating allows a replication target to immediately modify data at the source.This task is accomplished by using a trigger to run a distributed transaction.