My DS4 received a V Smile (console) for his birthday last March and a V Smile Pocket for Christmas this year. Honestly, he loves them both. Part of it is that he feels like his three older brothers (who, of course, are playing "real" video game systems like Xbox 360, PS2, GameCube, GameBoy, etc.).
But most of it is because this is a great system with fun (for kids his age) games that are easy to use. They're also educational (but don't tell any of my DS's that).
A note on the V Smile (console): We have an optional AC adaptor to save on battery costs and an optional additional controller to allow a second player to play.
A note on the V Smile Pocket: Two neat features about this toy -- (1) the device will output the game image on either its built in color LCD screen OR the INCLUDED connector cable can be connected to your TV's input RCA jacks for "big screen" gaming; (2) the controls on this toy can be switched around for ease of use by either right handed or left handed players (none of my DS's are left-handed but I still think this is a cool feature -- even though we won't ever be using it).
BOTH the V Smile and the V Smile Pocket use the same game cartridges without the need for any adaptor in either device.
As far as which one to get: It depends on your budget (the built-in LCD screen makes the V Smile Pocket about $30 more than the V Smile), the age of your child/children (the button-based controls on the V Smile Pocket require a bit more manual dexterity than the joystick of the V Smile), the "need" your children have for portable game play, and the need for two players being able to play (the V Smile can take a second joystick controller while the V Smile Pocket is for solo game play only).
-- Rob