To get this thread back on track:
I believe that the two are almost comparable. Sosa obviously had a huge cocaine production empire, and a big organization behind him. We saw it all. In GF, all we saw of Sollozzo was Sollozzo. But, as Hagen told the Don, "he's known as a top narcotics man." In the novel, Hagen says that he has contacts in the opium poppy fields in Turkey and plants in Sicily to convert opium to heroin. So we can infer that he was a big time operator. More important: both Sosa and Sollozzo wanted to establish distribution networks in the US. And both needed help from organized crime figures. If anything, Sollozzo showed more ambition, since he went right to the top: Vito Corleone. Sosa sought help from Frank, who was basically a wuss.