I like modrana, since it's free software.
Three things make sygic better currently though. - Voice navigation. Should be easy to fix through interfacing to espeak. I understand the author is already working on this. EDIT: Oh looking at post 165, maybe I haven't updated, it seems the espeak interface is working. Am gonna give it whirl...
- Fix the display so that vehicle is on the bottom as in the standard nav, so you see what's in front of you. Autorotate, so you're always looking forward. Auto reroute, without touching any controls. Should be easy to fix.
- Internet access. Given you use nav often in places you're not familiar with, many of the times it's gonna be while abroad, which makes it impossible to use now, since it doesn't do routing and uses google routes, so the web access would cost a fortune abroad.
The last one is the biggest problem.
I think it should be fixable - for instance by interfacing to routing abilities of navit - also free software, or using its routing algorhythms, don't know.
Until the last one is implemented, sygic will still be significantly better for navigation, unless you never navigate abroad, or in roaming, and have an unlimited data plan.