I am Zumo XT user since few years, but just recently became MRA user (I bought Gold membership). In general MRA is exactly what I needed for as how I do routes.
I do route planning on Windows Chrome webpage and minor adjustments on Chrome browser on android tablet (shortcut as an app to have full screen) that I take with me on longer few days trips. I then use andorid MRA app on my phone to export as version 1.1 and open with Garmin Drive, then bluetooth to export to Zumo XT. It works.
As someone suggested, Jheath's in Zumo forum is a must-read.
Also you have to have MRA gold membership because you want to use HERE maps.
You have to understand the difference between VIA (MRA = hand) and SHAPPING (MRA = tear) points, also to know that adding a waypoint for a city is not just search of city in the search bar, but to add waypoint directly to the road you want to drive by in that city... and use quite a lot of waypoints for a trip. And to have similar settings (avoid hightways, etc.) with MRA and Garmin XT...
A good tip is also about starting point... It should be a like 50 or 100 m in front of your actual start point so that you surely drive through it.
I also noticed that Zumo XT only show limited characters of route name in a Trip Planner. But if I name the route without spaces, I get to see longer names in Zumo XT, so it is better for organizing...
I am still learning, but so far... everything as planned