The updates in the 'Legacy Edition' of FIFA 14 include new kits and rosters, but not anything to do with gameplay, according to a Nintendo press release. Although Nintendo's details are noted for the 3DS version, EA is also releasing the Legacy Edition on Vita, PSP, and PS2, indicating the same lack of update on those platforms. EA previously confirmed to Pocket Gamer that FIFA 14 on Vita is a "reskin" (Pocket Gamer's words) of FIFA 13.
This story is itself a reskin of a previous story; FIFA 13 on Vita was a similarly limited update to FIFA Football, as was FIFA 13 to FIFA 12 on the Wii. In short, EA has plenty of previous experience in this particular area.
FIFA 14 hits North America tomorrow, and Europe on Friday, September 27. Despite the lack of gameplay additions, Nintendo is charging a full retail price of £40 (around $65) for the eShop version. If you feel that's worth it for new names and shirts, please enjoy.