fwiw a push type like the greddy type-s (rest it's soul) when set to it's weakest setting and installed on the hot side (close to the compressor) will never cause surge (because it hangs open even at idle).
the only reason not to run a bypass valve is if your demand for performance outweights the risks. In other words, in a competition setting, you want results and minimize failures. that said, having a bypass is an unnecessary risk in a competition, because you care less about protecting the parts, and more about winning.
In a daily driver setting, you want the bypass because it will extend the life of the turbocharger.
