Although the PS Vita doesn't come out until mid-February, it's not too soon to compare it to its closest competitor to see how it measures up.
Nintendo's 3DS has been out for nearly a year, but it's nearly $100 cheaper than when it came out, so now's an even better time to see which is better. The PS Vita has better graphics, a bigger screen (3DS has two screens), a touchscreen, front and back VGA cameras and is backward compatible with PlayStation Portable titles.
Nintendo 3DS offers glasses-free 3D, is backward-compatible with DS games and is cheaper. It doesn't have as many titles as some would prefer, but at least it's out now. You wouldn't have to wait another six weeks to get it. It also doesn't have a Game Boy Advantage cartridge slot. That means if you want to play one of your old games, you'll have to download it from Nintendo.
In reality, these devices are made for different audiences. Nintendo has games that people have grown up with and are very dedicated to. They also make more child-friendly games, and games that are for a general audience. PlayStation is obviously geared toward the hard-core gamer and is more popular with online gaming and first person shooter games. That is part of why Nintendo 3DS wins the recommendation. Playing Call of Duty online with the Vita seems like it would not be the best experience. Plus the touchscreen might make the controls a little wonky. There are other games to play on Vita, of course, but this does stick out as one notable example.
PS Vita works over Wi-Fi or AT&T's 3G network, has two analog sticks (one on either side of the screen), a five inch OLED screen with 960x544p resolution and even has touch control on the back of the device. It's $300 and goes on sale Feb. 22 in the U.S. Tell us in the comments if you are a mobile gamer.