Going by the philosophy two is one, and one is none, I travel with backups of anything important to get the job done. For car navigation, that means my iPhone 4 with Navigon and my TomTom 540TM XXL. The following is based on my observations based on using a dedicated TomTom unit versus the Navigon GPS navigation software on my iPhone 4.

Which is better for navigating during rush hour traffic?

For the most part, Navigon with live traffic subscription ($19.99) wins versus the TomTom traveling during congested / traffic heavy areas of LA / SD in a head to head. With the iPhone, internet access, and a traffic subscription plan, Navigon is notified of all traffic conditions along the route in real time.

In fact, if I just click to view the traffic (with no destination), it gives me a full report about traffic even up to 110 miles away and how bad the delay is.

TomTom with the FM receiver only receives traffic information that is broadcasted from sensors placed on major roadways when reception is within range. As such by the time the TomTom receives the traffic information, it may already be too late to respond or change route.

General navigation directions / routing:

With no traffic, I would say TomTom with the IQ routes wins. It's too bad that in LA, traffic is a major concern.

Navigon shows you a selection of three different routes to choose from, including one called MyRoute which is the one that you normally take. It gives you an estimate time to arrive for each as well as total miles travelled--very useful information.

TomTom just gives you what it considers the most optimal route (based on your preferences in the routing settings). And then, based on traffic information / IQ routes, it will then notify you if it finds an alternate route that will save you some more time. I setup my TomTom to tell me when it finds a better route and then ask me if I want to switch to the alternate. What it will say is something like, "...a new route has been found which will save you 30 minutes, would you like to take it? Then you can pick yes or no.

When Navigon finds a better route or further delays, it will also tell you that the arrival time / route has been recalculated based on new traffic information. Also it will tell you whether you are still on the fastest route (sometimes) or just switch you.

POI database:

POI searches with built-in Google search on Navigon ensured I got to the location I needed. TomTom was not able to find everything I needed in its limited POI database. To be fair though, I was looking up stuff on Yelp in areas I didn't know and may be new, so Navigon's built-in POIs probably wouldn't be able to find it either. In fact, TomTom appears to have a much larger and more comprehensive built-in POI. Still, through google local search (built-in to Navigon) I found everything I needed whereas the POIs on both were not up-to-date on several restaurants and banking locations in a recent trip.

TomTom was able to do other very useful things though. My favorite is being notified whenever I'm near a POI of interest, and if it's along the route. I often setup an alert to notify me whenever I'm near my bank's ATM and how far away the closest one would be. With TomTom's text to speech it tells me "Your Bank ATM is XXX feet away, next opportunity is XXX feet/miles..."

I also like to be able to pick a POI along the current route and add it to my destination. Navigon doesn't do that. I can also edit a POI directly on the TomTom as I choose - Navigon doesn't offer that. With Navigon, I can just add it as a favorite or remove from favorites.

TomTom provides free downloaded warnings of where all the traffic safety cams are and it appears to be regularly updated. Navigon does not.

Map Quality:

TomTom wins here so far. The maps from TomTom appear to be updated a lot more frequently, especially with the MapShare feature, which Navigon has attempted to try to incorporate by letting users report issues. With TomTom, I can report and download the updates almost immediately after hooking up to TomTom home. Furthermore, I can select what level of "moderating" I choose to accept - TomTom approved updates, updates that are trusted by most users, and even all updates submitted. With Navigon, I report it... and who knows when the next map update will incorporate it?

Ever since I started using Navigon it has always navigated the worst possible way to a local Fry's Electronics store. According to Navigon's navigation, there is only one way to enter the Fry's and that's through the opposite direction off the freeway (which isn't true). I've tried reporting it through Navigon and we shall see if it gets incorporated in the future.

So far, both Navigon and this TomTom unit will provide free map updates for the life of the product.

Speed

Navigon on iPhone 4 wins this round.

I'm really surprised at how slow the TomTom 540 series was. It reminds me of a really old Windows Mobile Pocket PC or a computer running really low on RAM. Punching in letters when entering addresses or POI looks gave me about a second delay or two with each entry.

Re-routing also takes longer than I'd like - often times the re-route is too slow when still driving in local traffic that it makes sense just to pull over where possible to let it finish re-routing.

I will say that about 2 years ago when I had my iPhone 3G, and ran the early version of Navigon on it - was much worse.

Navigon on the iPhone 4 isn't the speediest either. But it's at least twice as fast if not more.

I hear the latest generation of the TomTom GPS units are really fast and responsive, but I don't have one to compare or comment on that.

Visuals:

The resolution on the iPhone 4 is far superior, and I've downloaded and added in the extras for a sky simulation, panoramic 3D view etc.

The TomTom is much more customizable, and offers a superior heads up display that offers almost everything I want to know about the route / trip at a glance. I can customize the colors of the maps in ways Navigon doesn't even hint at being able to do.

I'm going to say that the size of the screen and what TomTom can give you at a glance is going to win this round.

Finger UI:

TomTom is safer to use while driving because the screen is larger, and the buttons are much bigger and colorful with icons.

With Navigon, it really can be a major safety risk trying to enter stuff unless you pull over. It can be done, and I do it more often than I like to admit - but unless you're stopped or violating the hands-free law in California and some states, it's best to keep your GPS input at a minimum.

Features:

TomTom wins. Bigger screen, more customizable options, IQ routes, POI alerts, safety camera alerts, more voices, more languages and countries supported even.

Navigon though has the much better live traffic, and integrated contacts address book which the 540 will never have.

Mount:

TomTom 540 mount is horrible. Not so much that it falls, but that the power connector / traffic receiver plugs directly into the unit making a quick release to stow away that much more difficult. Whereas with an active dock like that used on the older TomTom 9xx series or even the new series with the magnetic mount, it's a one step process. Just unmount - that's it!

iPhone 4 of course doesn't come with a car mount. My favorite choice right now for that is the Kensington Black SoundWave Sound Amplifying Car Mount for about $30. It too doesn't come with a simple all-in-one power plug, but that's optional and not necessary for all of the GPS functions to run. Although the GPS drain is pretty high so I end up plugging in anyway, but that's still less frustrating than plugging in the TomTom.

Price:

TomTom is much more affordable and cheaper to operate in the long run.

My Personal Preference:

Navigon on my iPhone 4. Why?

Here in California, traffic is a huge problem. Faster live traffic information is valuable!
I always have the iPhone 4 with me so it's more convenient to use.
The TomTom mount is horrible but necessary and third party mounts though improve the experience, still does nothing for the USB power / traffic receiver part.

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