Telenav employee here - we've been navigating exclusively on OSM since June for both iOS and Android (Scout Maps App). We also acquired Skobbler earlier in the year, which navigates using OSM if you're outside the US.
I've been wanting to look into the Scout/Skobbler SDK for a while now. I'll either be using that or Mapbox for some mobile/web apps. Do you have any insights to push me in your direction?
The points that differentiate us depend on your specific application. We have robust routing/turn by turn nav, offline maps, data visualization (heat maps) plus a whole bunch of other common features (custom styling, for example).
Definitely check out our dev site, which admittedly lacks some polish but is coming along (http://developer.skobbler.com/) and let me know if you'd like to talk to one of our SDK guys - they always want to talk to devs about their specific use cases.