First, make sure that the data plan fully covers you. Check three times. It's worth the extra time and money to be sure!
In my opinion, Google Maps can't be beat. I have used both in Europe and after a few minutes of BB maps I switched back to Google Maps. The routing is better, it's faster and the satellite view is superb. In comparison to something like an iPod Touch on wi-fi, both apps are slow on Blackberry.
Google Maps is also quite special in that you can route three ways: Driving, transit and walking.
As for the GPS, the Tour has a decent receiver but like most Blackberries it can get lost easier then a dedicated GPS when it has an obstructed view. The GPS is also disabled if you have no data service - so you can't drop waypoints on a hiking trail if you don't have cell service.
Hope that helps.
Pete