If your clients are deployed within intranet then choose transport security
Jason Taylor, Prashant Bansode, Carlos Farre, Madhu Sundararajan, Steve Gregersen
Use transport security when your clients deployed within intranet, as it provides point to point security and is performant compared to Message Security.
In an intranet you have control on the communication between client and service, and hence very few chances of having any intermediaries which might break the transport security. You can use netTCPbinding which by default uses binary encoding and transport