IMPREZvWRX is mostly correct. If the SAMCO hoses were the same shape (specifically the Y-Pipe) there would be little to no difference. However, if you look at the plastic Y-Pipe going from the Turbo to the Intercooler you'll notice it has some restriction to it. This creates greater head loss in the piping. You want to lower the resistance as much as possible so the turbo doesn't have to work as hard to spool up. The hose between the throttle body and the intercooler....I have a hard time believing that does anything. The BOV hose, I can't even speculate whether or not that does much.
Every little bit helps, I have them on my car, not sure it was that noticeable. I tried to monitor spoolup and the like afterwards. I'd like to claim it lowers spoolup, albeit a little, however I have no hard data to back that up with.