We have also used Microsoft Streets and Trips for several years with the little GPS module. I like the ability to use S & T on my laptop to plan a trip, modify routes, identify points of interest along the way, etc. However, it is a bit dopey to have the laptop on the dash...not impossible but not as easy as it sounds on our current coach.
So, we recently got the Garmin DZL760 GPS which has a large screen and many useful features for RVr's. While it is developed for the commercial truck driver, it works very well for RV use. In fact, we have learned to develop a trip on the laptop with Streets and Trips, then download the trip to the Garmin. Then we use the Garmin to help keep us on the desired route.
Our coach also has a Pioneer GPS built into the dash radio/back up camera monitor. We recently got this coach so I have little experience with the Pioneer but I plan to see if Street and Trips routes can be downloaded to the Pioneer.
There are many GPS options so you have many choices. However, we have learned that any of them will occasionally 'lose its mind' and try to send you on a rabbit trail.