All the LPFP has to do is supply the fuel to the HPFP, the HPFP is the one doing the hard work, and just because of the DI system. So all that's needed from the LPFP is to supply X amount of fuel. So in reality, it is pretty much the same. New GM LT Gen engines have DI as well, and the upgrade to the LPFP is about as easy as it was for the LS.
From what I can understand, it takes about the same amount of fuel (slightly more in the 4cyl) to produce the same horsepower. This is why a lot of turbo 4 cyl have very similar mpg as the 8 cyl counterparts, which is why generally the same pump used in a boosted V8 also works on a boosted 4 cyl.
But, what I was referring to was the difference or the amount of work required to upgrade the LPFP in the GTI vs the simplicity of the GM system.