Co-pilot, the reason I choose this over Ndrive and google is beacuase:
Google is good if you have data connection all the time, but too robotity in voice.
Ndrive is excellent but no turn-by-turn, only 'funny' voices and crappy standard ones.
With co-pilot I can use my installed loquendo TTS engine with 'Susan', which is rather life like, for near perfect TBT, although she is a yank.