I believe the Handhelds Have to co-exist, this isn't a console war when the majority of the games out there are on both systems.
The DS and PSP always had something to go back to and I can't determine which was better of the two without making them even.
The 3DS and PSV are the same case, with only 2 games in common (MGS3 and maybe Monster Hunter 3) They will both be very different from each other.
But the one thing that is more effective than anything is advertisement.
If God of War 3 Sold that much, it was all advertisement (GoW3 was a complete crock of shit with polished graphics), Whilst Infamous (fucking superior) is relatively in the shadows.
In the Vita's Cause, Uncharted, a Series where the Story is more important and remebered than the gameplay is a very unwise choice to flagship.
oh, the 3DS has a problem too, Where the hell is Kid Icarus? that was the FIRST 3DS title I've seen before it's release.
Both are sprting very good titles, It really sucks that they are in the awkward state of ports and remakes for the sake of sales since give or take 10 original titles aren't enough to sell the handheld alone to a wide audience.
Since the 3DS has those guaranteed titles, and Smash Bros 4 (along with wii U) plus great new ones coming soon I'm sold
Vita has Bioshock and Ys, LBP, Like the PSP, its gonna need a few more titles, but Its still gonna be a buy.
Note: SHAME on you Square-Enix, Pikmin for the Vita? C'mon! you guys are supposed to make Good Handheld games!