I like Scope Coat but that just maybe personal preference as I've never used the Vortex covers.
The Vortex Defender scope mounts are fantastic, and better than Butler Creeks by a country mile. I’ve had a set for three years, and have held up to some pretty abusive country in the process.
Dave
Mine seem to work just fine but I only own 1 Vortex scope, ymmv.