Don't know what the Stagea one is like to install, but obviously it would be different. Just as the Silvia one is different.
The Walbro is a lot easier to install than the Bosch that is for sure. Definetely not as easy as the Tomei/Nismo one given that you literally pull the entire old fuel pump assembely out of the fuel tank and put the new unit in and plug it back in and you are done.
The Walbros are a lot more sensitive to flow rates vs voltage and therefore some cars require rewiring to ensure they get 14V.
As I said, if you are confident in what you are doing get the cheaper fuel pump. I am just saying the Tomei/Nismo is worth the money given how reliable and easy the install is.
Your choice.