After a strong showing in Japan at launch, the PlayStation Vita has entered it's second straight week of sharp decline, selling below both the Nintendo 3DS and Sony PSP. The system sold an impressive 324,859 in its launch week, but tumbled down to 72,479 in its second week and 42,648 this week, according to the latest MediaCreate numbers.

Andriasang reports that the figures from December 26 through January 1 show the 3DS almost beating all other hardware platforms combined, and taking five of the top ten software sales spots. No Vita games placed in the top ten, echoing a trend from the week prior. The Vita had a lower attach rate at launch as well, but that was explained as a product of its downloadable environment. Sony was quick to state that downloads were "exceeding expectations."

As Joystiq notes, this makes for an interesting contrast against the Nintendo 3DS. Nintendo's handheld fizzled quickly and resulted in an unprecedented price drop. But the 3DS' second week in Japan sold 209,623 units, and its third week slowed to 96,463 units. If it was considered a flop, the Vita moving less than half those amounts during its second and third weeks aren't optimistic signs.

As in the US release plans, the Japanese price of the cheaper Wi-Fi PlayStation Vita is roughly equivalent to the 3DS launch price -- both at 25,000 yen. The more expensive 3G model carries an MSRP approximately 30,000 yen, just as the US 3G model will be priced $50 higher than its Wi-Fi cousin.