The udpnode stuff is not exposed on the public FIBRE instances because I dont significantly trust that there isnt some bug in the implementation somewhere which could cause the nodes to crash with data sent corrupted in some way. The other option (the fibrenetworkclient thing from my RelayNode github) exists only to make sure connections stay up reliably. See two posts up (where we talked about https://github.com/bitcoin/bitcoin/pull/9319), which will make -addnode a much more reliable "keep this connection open" option in Bitcoin Core 0.14. fibrenetworkclient shouldn't make any performance difference at all.