I traditionally have used Garmin Connect’s route editor to create my routes. It is far from bug free, but I’ve learned the quirks and I can make it work. I just tried to re-create one of my usual routes in Strava Routes and had to quit after just a few minutes of frustration.
I’m fortunate to have some great paved bike paths, that are long established. Garmin generally uses them just fine. Strava kept giving me convoluted routes and generally got confused. For example, one part of the route follows a river. I dropped a point along the path on the river – Strava tried to put me on the other side of the river! The dot on the right is where I put the point; the endpoint is where Strava placed it.
That’s roughly a 10-15m error.