If the machines at each end are reasonably powerful (ie not netbooks, NAS boxes, toasters, etc), then I would expect all protocols which work over TCP to be much the same speed at transferring bulk data. The application protocol's job is really just to fill a buffer for TCP to transfer, so as long as they can keep it full, TCP will set the pace.
Protocols which do compression or encryption may bottleneck at the CPU on less powerful machines. My netbook does FTP much faster than SCP.
rsync does clever things to transmit incremental changes quickly, but for bulk transfers it has no advantage over dumber protocols.
