Seeing as the generator in question can put out only 120 volts, protection from a "open neutral" (the source of 240 volts) is not needed.
This thread is not about surge suppression but, here are my thoughts.
My own opinion is that the PI and SG are better only at the top of the line. My own feeling is they sell assembled parts and mark up the cost 1000%. They do use mov's as well.
Anyone who plugs in without checking voltage under load is taking a risk. Top of the line PI and SG do not check voltage under load.
I do have surge thanks to mexicowanderer, and that surge I'm told, is far better than PI or SG offer.