If you're the kind of Spira-nut who's getting both versions, the good news for you is the game supports cross-saving, meaning you can pick up your Vita progress when switching to PS3, and vice versa. A word of warning on the physical version: the Vita cartridge includes Final Fantasy X, and a voucher to download Final Fantasy X-2 from the PlayStation Store - the PS3 disc will have both games on it. The two remasters are also coming to the PlayStation Store in a combo pack.
Square Enix also announced a PS3 Collector's Edition today, featuring a 40-page hardcover art book, a FFX HD Remaster soundtrack, and five art lithographs. The CE's going at the price of $80, and it's available only at Square Enix's online store.