I currently use a Garmin XT2. Been using Garmin devices for years (Street Pilot III, Zumo 600, Zumo 595, Nuvi 30).
Started out using Basecamp for routing and I'd consider myself proficient in it. Learning curve is a bit steep, but having a database as a backend is a great feature. Unfortunately Garmin isn't maintaining Basecamp anymore and there haven't been any updates to the software for at least three years. Routing software is fairly complex and I can't trust any complex piece of software that isn't being maintained. I've migrated to using MRA or MRA Routeplanner. While it doesn't store the waypoints in a database backend, the software works and is maintained.
I've also been using Garmin Tread to transfer routes from MRA to the Zumo XT2, but the Tread software is buggy. There have been many issues reported with Tread on the GPS forums.
Every GPS device/software is going to have minor differences in how they calculate the route.
My one recommendation is to include a TRACK with the route. Hence, people can compare the track with the route and make changes to the route in their software based on the track.
Oh... current map update Is City Navigator North America 2027.1