Advice: how much memory?

[jsw]

GPS navigation apps, on the other hand, will very likely be stored locally.

Actually with true turn by turn GPS navigation software by Tomtom and Navigon coming out this month Maps will be stored on your iphone.

Point taken. Apologies for my ignorance.

 

[Night Spring]

After looking around the TomTom website, it seems their map for North America is around 2GB. So 16GB should be enough, unless you want to load maps for the entire world onto your iPhone at once.