I have all 5 games for the DS, and I can honestly say, Ace Attorney one of the best game series I've ever played. The characters, the cases, the plot twists, the puzzles... It's all phenomenal. I wasn't aware that it was for the Wii though. Anyways, I highly recommend it. Especially since you are a fan of the PL games. Hopefully the YouTube videos you saw didn't give away too many spoilers. I recommend playing the games in order too. You won't understand the plot if you don't play it in order. (Ace Attorney, Justice For All, Trials and Tribulations). Apollo Justice is kinda... meh. Not the same. I don't like Ace Attorney: Investigations either, it's my least favorite of the series. The Phoenix games are the best, especially the first and third. Also, I'd prefer the DS version. Getting to dust for fingerprints with the stylus and blow away the dust with the DS's mic is awesome. Not to mention getting to actually yell "Objection!".
As you mentioned, there is blood, an occasional "damn" or "hell", but nothing too much. It's only rated Teen after all.
Ace Attorney: Investigations 2 has been released in Japan, but it's not getting a worldwide release. It's rumored to be the end of the Ace Attorney series outside of Japan.