Each has their strengths and weaknesses. The phrase "Let those who ride decide" applies here, but not in the traditional sense. When I was trying to blast through Dallas traffic in heavy traffic in rain, being able to use the 'old tech' Garmin with gloves in rain helped a lot. And I can still do Pandora from my phone to my Sena.
If you're happy with the way you do it, that's good. I lead a lot of rides (this year, it was 3k miles to Austin and back to see the MotoGP and ride Hill Country) and I make routes, then export and email to others who download to their GPS also, so everybody has the route and turns don't surprise people. I also did a ride from Peoria to Arkansas, 4 days, 1700 miles of twisty bits, same deal, lay out the routes in advance, export the files and send to everybody so they can load. Works well.
I will say that the software that came with my Zumo 220 (Mapsource) is clunky in some ways, but works well in others. I set a bunch of waypoints at specific locations, then link them all with a route, so we go exactly where I want to go, down the good roads and not the more direct route Google maps does. If there was a slicker way to use Google maps so make a file importable into my GPS, I might be up for that. Although sometimes Google maps gets confused and I end up with purple route lines in wacky places. In the Garmin software, I just delete the waypoint and route info and go from there. But the Mapsource has limitations, I'm sure its database is out of date but has been fine, never gotten a bum steer in 10k miles of touring with it. But I am open to slicker/easier/mo better ways of doing things.