I've used a laptop, the GPS antenna puck, and various software. It's nice when navigating city streets to an address to have a large screen. Garmin nRoute has good voice prompting and a host of navigation features that make routes totally usable for larger vehicles. I bought nRoute and the antenna years ago so don't know if that system is still available. I also have MS Streets and Trips loaded on the laptop for additional maps and features.
Since I don't deploy the GPS laptop except for longer trips, I use my Iphone for local navigation. Both work and both have different functionality.