I'm saying it's very likely you should be looking into alternative approaches if the fast path performance is genuinely your bottleneck, and that in my experience it's overwhelmingly likely that that's not the case. Most likely you're doing too many dynamic memory allocations to begin with. Note that even if you invoke the fast path 20x more often than the slow path, it's still going to be peanuts if your slow path is 1000x slower.

Best way to support your point would be to illustrate with realistic examples instead of hypotheticals. Otherwise this is like the JIT vs. AOT debate that always goes nowhere because the JIT side only ever uses hypotheticals to support their case.