There have been a lot of posts about this issue, and yet I'll try another one.
When I import a track with built-in elevation data, Garmin Connect (GC) totally replaces it with its own. Not only I find it really inaccurate, it also ruins my own precise elevation profile. For instance, I have a track recorded with some device using barometric altimeter in heavily rugged relief, and I want to keep that accurate data instead of applying some automatic "smoothed" DEM.
The only reason I'm forced to use GC is the course points - a feature I find really useful. Unfortunately, for now, Garmin Explore (GE) doesn't allow me to drop course points on the imported track like in GC. I understand there are workarounds like plotaroute and cable transferring *fit files, but they are not really convenient.
Moreover, there is a significant difference between the elevation profile generated by GE and GC, which I do not understand. And I find the GE elevation profile to be far more accurate.
For a device marked as an outdoor recreation unit, such a lack of basic file handling control is unacceptable.
