TBH, it's hard to imagine why Vita would be doing better right now.  3DS had a price cut soon after launch and is now stablized with key titles released.  It's now an attractive purchase and embedded in the market.  The Vita is new, has an average to decent set of titles none of which are killer locally, is still at launch price point and is in the early adopter phase before any stabilization of the platform.

The ratio of 3DS to DS shows how much demand has transfered plus the device has genuine excitement now.  The ratio of PSP to 3DS shows much of the demand for Sony's handheld device/games still rests with the PSP with only a partial transfer of demand to Vita.

So, Monster Hunter 3G surpassed the Wii version, and will likely do, what 1.5m?

Other than the obvious monster numbers of the 3DS, I find quite interesting the SW numbers for the Wii.

The 3 brothers of doom are still doing their magic. Good PS3, PSP and Wii numbers. 

Last year numbers...

DS: 87,118
PS3: 59,612
Wii: 56,547
PSP: 32,841
360: 3,859
PS2: 2,547

YoY

DS down 91%
PS3 up 25%
Wii down 12%
PSP up 116%
360 down 29%
PS2 down 48%

PS3 and PSP are doing a GREAT yoy job in Japan.

PSP almost 40k up on last year
PS3 almost 16k up on last year
Those are some great numbers for both consoles.

3DS still a monster

The Vita will continue to sell "poorly" until they have games that Japanese like, it is that simple.

Wii continue to fall on last years numbers and will continue to do so, drastically this year.

GrrrrreAT sales! Mario 3DL will surely be the best selling 3D Mario ever!

I would like to see how Vita is holding up against the first weeks of PSP.

Roughly tied this week, next week PSP will be greater. 

After four weeks on sale:
PSP - 482,252
Vita - 482.901

Source: Neogaf poster in this thread: http://www.neogaf.com/forum/showthread.php?t=458546

WOW. EPIC TIE.

3DS is dominating the scene, not a surprise. We'll see during the year what they'll get with the new software we're waiting for (RE Revalations and all the Nintendo hits).

The vita is in real trouble. Reasonable said it is still at launch price. Not true. A huge amount of retailers have already dropped the price of the 3G. Around a 15-20% price drop at most stores. That's pretty considerable.

These sales are already after a bit of a price drop from retailers.

The problem the vita has as well is with the 3DS we knew Nintendo could afford to drop the price. With Sony I'm really not sure they can manage it.

Also with the 3ds we knew that Zelda:OoT, Mario Kart, Mario and Monster hunter were coming and they would help sales massively. For Vita what game is going to help? There are no big titles for months. In fact I can't even think of a big title for the Japanese market this entire year. Anyone think of one?