The only real difference than is Span. The prospects dealt by the Mariners were weak, to be kindMoore was ranked 8th in the Mariners farm in mid-season 2017 by some and Romero was outside the top 20 of what was also a bottom third farm system. And citing their post-trade accomplishments doesn’t change what their status at the time of deal was. It’s not like improving is something limited to Mariner minor leaguers.
Actually predicting a trade like this is difficult, but plenty of deals are made because GMs often value players differently than fans and scouting organizations. The Sox do lack the prospects to add major pieces, but could certainly add a reliever similar to Smith (who, again, has only one year of control left) using some combination of players like Chavis, Dalbec and Hernandez, whose status has apparently risen with his recent AFL success.