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WiiU is the hot new item, but 3DS already has an established library. If you have the original I wouldn't upgrade, but if you don't I might just get it. There's also some great holiday deals on 3DS which you won't find for the wii-U, but that probably isn't even a factor in your choice.

Try to think of what games you want for either system and how much use you'll get out of either.

I like to get a backlog of good games so I can just perpetually buy good games at heavy discounts.

3DS, and it's no contest. The Wii U needs a year to mature.

Like Kegan said, do you have the original 3DS already? If so, it might not be worth upgrading when you could get a new home console. That said, if you don't have a 3DS or the Wii U, I'd go for the 3DS simply to have more games to play. The Wii U is a blast, especially with Nintendo Land, but that's mostly if you have others to play it with.

BUT if you're going to be getting one or the other for Christmas, go for the Wii U and save up for an XL. That's a price difference of $150. Good games are [scheduled to be] coming out for each in the first half of next year; Pikmin 3 and Animal Crossing New Leaf are the two I'm most excited for, so look to see what games you'd be missing out on, too.