I won’t go into how to use the software. There is plenty of documentation to help you in that respect. Suffice to say that it is very intuitive, but you will need to spend some time playing before you rely on it. You don’t want to get stuck not knowing what you’re doing. But it’s not difficult. After only a short time I was able to very quickly add waypoints for interesting things we found along the way. And entering detailed information about each waypoint is very simple with the pop-up on-screen keyboard. It’s probably best not to do this while you’re trying to drive though. Wait until you’ve stopped or you might find yourself creating your own tracks!
Both apps offer beautifully rendered 3G maps that can be viewed vertically or horizontally, and a very convenient way to enter a new address or find a point of interest (POI). They come with good databases of POIs, too. I was in a few rather remote areas and was able to find what I needed. However, the database is not very updated--twice, both apps took me to restaurants and bars in La Cross, Wis., that were no longer there. Unfortunately, you can't tab on the listed POI to call its phone number, which defeats the main purpose of the iPhone, which is, after all, a phone.
One of the biggest problems I face using Garmn in Thailand is in entering an address. 99 times out of 100 it rejects or denies any knowledge of the place name entered . This means effectively that I have to find the new destination pretty much by luck, good judgement and a sprinkling of local knowledge . Do any of the apps you mention have a more “user friendly” interface for finding new locations? In Thailand you can only get official map details from one company Esri and pay an additional £50+/- for the pleasure of doing so.