Four local runtimes, the same weights, four different prompts going in and four different answers to whether a tool call comes back parsed. None of that is throughput, and throughput is the only axis anyone compares.
Three of these four constrain the sampler so invalid output cannot be produced, and the choice between them collapses to one question: do your schemas repeat? The fourth does something categorically different, and it is the only one that can enforce the rules that actually break agents — because a grammar guarantees the enum is one of five values and says nothing about which.