Actually, Terra spoils Ven's story quite a bit, so I would suggest VTA.
Ven doesn't spoil anything, Terra spoils Ven, and Aqua slightly spoils Ven's, so in this way no one spoils anyone else. Seriously, Terra's story hardcore spoils Ven's story, so I would highly suggest doing Ven's story before Terra's. I know TVA is recommended and all, but it doesn't make near as much sense as VTA. Plus, with VTA, there's always a bit of suspense because you (like Ven), don't actually know what Terra is doing in the worlds. If you get Terra's story first, you kinda get the "don't worry about it, Ven, he's fine" feeling when Ven is desperately searching for Terra.
For those like me who are spoiled:MX literally tells Terra exactly what Ven is and how he came to exist. This ruins Ven's story almost completely. And Aqua and Ven share an ending, so in Aqua's ending you will know exactly how Ven ends up, though you won't quite understand why.
That's my 2 cents. I don't have a PSP, so I can't play it myself, but I really want to stress how much better VTA is than TVA. Honestly, TVA is probably the worst way to play if all you care about is story.