There is something people don't seem to understand. If they go back to growls, they will sound even worse. Mikael cannot growl well anymore and their most recent live record is a clear representation of that. And nowadays, when they are playing their old songs, they sound like a cover band. They play slower, less intense/agressive, less energy, less intensity on the growls, less distortion. Mikael doesnt hold the growls for long either, which makes it sound lazy, less evil, less enthusiasm.
So growls, no thanks.
On the other hand his singing only got better and better and he should keep going with it.