In the end you'll have to figure it out for yourself, but I know I prefer the Vita, as I've tried both systems in stores. The 3DS is ok, it's pretty cool with its 3D effect. But I like the Vita a lot better. But just know that you may be different, you have to choose. Try them out in stores if you can, at Best Buy, Target, or Gamestop.
Here's my pros and cons for the Vita system. This is what I think of it.
+ Big, very sharp, colorful screen. The Vita has a 5 inch OLED screen. It's big, and the OLED technology allows it to display more of the color gamut (which makes it more vivid), while running at lower power consumption. The high resolution of the screen makes it very sharp, very pleasing to the eye.
+ Powerful hardware inside. The Vita uses a quad-core (4-core) cpu main processor -- one of the latest mobile cpus -- and a quad-core gpu graphics processor.
A good illustration between the 3DS's power and the Vita's power is in the graphics processing capability of each.
The 3DS handles around 15.3 Mpolygon/s (million polygons per second) and pixel fill rates of 800 Mpixel/s (mega pixels).
The Vita handles at around 133 Mpolygon/s with pixel fill rates of 4 Gpixel/s (giga pixels).
So you can see the Vita is a lot more powerful. Even if Nintendo unlocked the gpu of the 3DS's clock frequency to the max of 400 MHz, it still would not come anywhere near the Vita's processing power. And this is the baseline clock frequency of the Vita, which is estimated at 200 MHz (just like the 3DS). If the Vita actually is higher-clocked than that, it would make it even more powerful.
+ Vita's control inputs. The Vita has dual analog sticks, along with dual touch screens, which add to the control options in games. The 3DS only has one analog stick, and has to use the 2nd screen for a second stick. A minor setback but it works.
+ Good games for the Vita. The Vita has a lot of AAA games coming for it. Call of Duty, Resistance, Bioshock, and Grand Theft Auto are just a few. Most of the best Nintendo games come straight from Nintendo. But that's the thing, many people like Nintendo's games so they buy their consoles.
+ Online features. The Vita uses Wifi or 3G (in 3G/Wifi models) to connect to the internet. And in this many games feature online multiplayer, where you can play with usually three other people. The 3DS has this I believe to some degree; some games have the multiplayer option, I'm almost sure of.
+ Apps. Along with the 3DS, the Vita has Netflix. I'm not sure what other social network or other apps the 3DS has, but I know the Vita has Facebook, Flickr, foursquare, Twitter, Painting app, and Skype, so far. These add to the versatility of the Vita.
+ The system is completely quiet. Unlike the previous PSP, the Vita makes no sound. The PSP has a loud loading disc drive, which was very unattractive. The Vita doesn't have this problem, because it uses flash-based memory this time.
- One PSN account per Vita. Sony said they wanted the Vita to be used by only one person, and that sucks. The previous PSP was like that, but it would've been nice to have your sister or brother to be able to have their own account on your Vita, without disturbing your account. But that's what Sony decided to do, and we can't change it.
- In some games, graphics could be better. It's up to game developers to make a game's graphics optimized for the Vita's hardware. The Vita has great potential, which is seen in the games Uncharted and Unit 13, but it's up to the developers to fashion the graphics around this potential.
- An either-way entry for the power cable. The USB power cable is only meant to go in one way, as is every electronic device today, but it can also fit in the other way. This is a huge design flaw. I'm not sure if you'll break the chip in the port if you fit it in that way, but it can be done. Gamespot.com has said that it can fit either way, but I've never done it. Though fitting it in the right way is the only way it will charge the Vita.