One less sticker to peel off, in my opinion!
Serously - Sony probably paid more to nVidia, and got some stickers to stick on their product, to make you and me think that there's something special inside there that the other one doesn't have. They both claim to have the same make/model of video card, and so they probably do.
If you're not sure, bring a LiveCD with you to the store and run `lspci` on it to make sure it's the advertised nvidia card. Or, as Drakeo wrote, they will either show you, or let you find out for yourself, what's inside the machine, before you buy.