which is better sockets/socketchannel why

Better for what? They both work. Sockets are simple but only support blocking operations. SocketChannels are about ten times as complex to use but they support non-blocking and multiplexed I/O and also various types of direct and mapped buffering so they can also imply less data movement.

Performance is mostly determined by the network, so they would both be the same. I would start with Sockets and then see if you have a scalability problem or data copying bottleneck.