The 3G model which was overstocked was cleared with price reductions and memcard bundles. There's no reason to believe that retailers have a large stock of Vitas now they need to get rid off.
And no, I didn't make your point. Retailers have no alternative to the 3DS if their motive is to sabotage DD.
Chain retailers would have a fair bit of stock to move between all of their locations, yes. But it's not a matter of stock laying around somewhere, either.
It's a tricky scenario for retailers, they have to buy an amount that prevents an out-of-stock scenario but doesn't leave them with a surplus of units.
In retail, any stock that sits for any length of time becomes a strong liability. Bomba pricing on games happens because of this perceived liability, and hardware can't be moved in such a fashion typically because of slim-to-nil margin. That 3G model clearance you mentioned was likely done by selling the product at or below cost to get it out the door, since it's better to recover your costs than let a product sit on a shelf.
Since hardware makers
RELY on retail to push a product, as TV and print marketing from the hardware maker only accounts for a percentage of purchasing motivation compared to retail promotion in the video games sector, the next time that retailer goes to Sony with smaller orders to fill on hardware, their Sony rep is going to say "sales are down, we NEED you to push this product".
THIS is where the difference is made.
The retailer will say "sales are slow, game sales are down because of that and you're undercutting us offering digital for cheaper than we can sell games where we make all our margins in this sector.
What's in it for me to promote something that makes my company less money?" And the retailer would be completely within their right to do so.
So yeah, a lack of retailer incentive to push the product DOES get attributed to this issue. Vita is an example of a situation when retail partners are less willing to accommodate the needs of the vendor to sell the product because the hardware vendor is eroding their bottom line from the get-go.
If Nintendo went in the same direction, retailers would stop promoting EITHER handheld in that case and, in the case of major retailers that sell different products and make up the majority of game hardware sales, would say "I'd recommend a smartphone instead" and point them to that section of the retail outlet.