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I am sure someone on here will know the full story, but to my understanding Sportful is a sort of in-store brand from an Italian conglomerate of factories that make kit for Assos and Castelli. Their NoRain fabric is rumoured to be gabba fabric but re-branded and then sold for roughly 2/3 of the price.
I've not had the chance to compare, as I never owned gabba, but I own some bits of Sportful NoRain kit and have no complaints.
On a general note I reckon Sportful is superb value for money. If you've narrowed your options down to A, B and Sportful, and they come out quite equal, then just take the Sportful one.