I'm getting Ultimate Ninja Storm.
They have the same number of characters, but I doubt Broken Bond will have older characters such as Zabuza or Haku like Ultimate Ninja Storm probably will, and they're a couple of my personal favorites.
Furthermore, UNS covers the entire Naruto story up until the end of the Sasuke Retrieval arc whereas the Broken Bond simply picks up where the last game left off with the Return of Itachi, Seach for Tsunade, and Sasuke Retrieval arcs.
Also, as far as graphics go, I feel that Broken Bond's cel-shaded characters look somewhat goofy on the game's fairly realistic backgrounds compared to Ninja Storm's characters and backgrounds that look like they were both taken straight from the anime.