IB and RoCE are not intended to compete
Alien Anthropologist is quite correct. IB has traditionally led Enet by several generations in bandwidth and latency and has always been the lowest price/performance.
That said, there are environments where it is simply not possible to transition to a new IB infrastructure. For example, many commercial enterprise data centers could benefit from IB's value propositions other than its raw bandwidths and industry leading latencies. For example, RoCE can bring major decreases in CPU utilization and reductions in memory bandwidith demand to an existing Ethernet infrastructure thus significantly reducing the number of servers required and reducing power consumption and footprint. These are the types of markets at which RoCE is aimed. RoCE does not compete with IB in terms of pure horsepower or price/performance. The fact that RoCE delivers 'IB-like' latencies is a very nice advantage.
Chief Scientist, System Fabric Works, Inc.
Chair, IBTA RoCE Technical Working Group