The main advantage is: the congestion control! With MPTCP you could deal with congestion at the transport level. Meaning, if you have three flow MPTCP will select the best (less RTT, space in the win, etc..) link to send datas, where the bonding is just balancing with a XOR or a round robin. This is definitely a big advantage, not only in datacenters but if you have a 3G and a WiFi connection. More about the congestion control: http://tools.ietf.org/html/draft-ietf-mptcp-congestion