congestion

Both run at the same port speed, so the discount is not buying slower hardware. It is buying a different operational model and a different failure mode, and whether that is worth 15 percent depends on what your team already runs and what the fabric has to carry.

Both carry RDMA at the same line rate. One arrives lossless because the transport was designed that way, the other becomes lossless only if a set of switch settings is correct on every port. What that difference costs in operations, what it saves in money and hiring, and the fleet size where the answer flips.

Thirty-two senders aimed at one port fill a switch buffer in microseconds, and what happens next depends on which of two mechanisms fires first. The buffer arithmetic, why the slow mechanism is the safe one and the fast one is the dangerous one, and the counters that tell you which is happening.