Having used both, I was surprised to find that Sprint Navigation performed much better than Google Navigation.
1. In both apps you can search for an address you already know.
But say you wanted to find a list of a certain kind of store near you e.g Pharmacy, post office, chinese food; you have the ability to search by category in Sprint Navigation.
2. You can use the 'speak destination/type destination' buttons in Google Navigation and instead of an address just say a category and you get a list of results in that category and their addresses that are close to you.
However in Sprint Navigation, you get a list of results, their addresses, phone numbers and their approximate distance from your location in miles. This is extremely helpful when you don't know the area or recognize the addresses.
3. Additionally, in Sprint Navigation, you can search for categories in locations other than your current location.
4. I performed a test in my city.
I searched for post office in Google Nav and it gave me a list of addresses I had no idea of. so I picked the first one and followed the directions. It led me to a driving range!
I went back to my original location, loaded Sprint Navigation and did a category search for Post Office. I got the address, phone number and miles for each one close to me. I picked one and it led me right to the post office.
As far as functionality and ease-of-use goes, Sprint Navigation is my nav app of choice on the EVO.