Sorry, I do not know is there's an operation, in which WinSCP is 400% slower than FileZilla.
FileZilla is known to be somewhat faster in some operations. In general they focus on speed, while we focus on functionality.
Sorry for offtopic. I don't see any general purpose section. I have been using WinSCP for many years personally. And at work we have it as a standard for SFTP/SCP. But some users cling to FileZilla. Probably mostly because of familiarity. But sometimes i hear claims that seem strange. I have never tried to do some sort of benchmarking between two. But i wonder is there a known thing that something might operate slower in WinSCP? I'm thinking maybe operating with lots of small files, thousands of files or on contrary with big files? It sounds like an exaggeration when a user claims it is 400% slower than another client, but they are still coming from somewhere with this conclusion.