If Godbout takes to the Sox bat speed program I think you could be right, but in the absence of that I'm not sure his poor bat speed is going to translate to the major league level, he might not be anything more than a slap hitter.
Arias has a good hit tool too but same questions around his power potential. At 20 years old, and two full years younger than Godbout I'd say there's a better chance that Arias is going to grow, fill out, and add size more than Godbout will. I'm not saying Godbout isn't going to add strength (which isn't the same exact thing as size) just that Arias has more room to fill out. They both might rise to that challenge.
IF they both do solve these issues, I think I'm going with Arias because he has a much higher defensive ceiling.