Just installed an official FRS Headunit that came from the dealer with the Scion Nav system. It's an ebay junkyard purchase. You would laugh if you saw how many tamper proof stickers and paint on the screws they put on it, guess the got ebay screwed before. I'm going to play with it for a week or two. So far I like Entune better. AHA fuel function sucks and nearby leaves a lot to be desired. Seems like the Scion system has more POI icons on the map. I'll probably will turn most of them off. Over all, there is not a lot thats different between the systems. Entune has a few apps that Toyota installs that tend to be clunky and slow because of the slow processors. Scion depends on AHA app which is made by Harmon, the makers of the unit. The Nav and voice operations are very similar.
If you want factory Nav, go to Ebay and hunt down a headunit that includes the nav unit. I seem to find better deals on the combo. People selling the Nav unit by itself seem to charge the same as getting both together, May as well get both and try to resell the headunit by itself to get some cash back. In my opinion just get which ever pops up first, AHA or Entune. Yes I think Entune is better but not by a heck of a lot.
I think I am going to swing by my dealer tomorrow and see if I can get an update for the Scion Nav unit. I tried doing an update with my Entune 5.2 software but it doesn't work. So there is no quick and easy way to convert the AHA to Entune.