Aggregating data from r/PSP, r/Roms, and PSPISO.ru , the consensus is overwhelming. In a poll conducted on a major retro gaming forum in 2023 with 1,200+ respondents asking "Which FIFA 16 PSP version is best?" :
Fully updated transfers, including major European and Latin American league squads relevant to the 2015/2016 season.
The "Español" versions are highly sought after because they often include localized features that improve the experience:
Accurate home, away, and third kits for La Liga and other major leagues.