VIVO is Video In, Video Out. If you'd like some video editing capabilities, that would be a nice feature.
The 128MB Ti4200 typically have the memory clocked a little slower than the 64MB versions.
If the price between the 2 is minimal, the 128MB might be worth it. If the price is much more than $20, it's probably better to get the 64MB version instead.
However, if you actually need some video input, the extra cash would be well spent as you wouldn't need an extra card.