Well I suppose this could be a speakers corner topic
since you are seeking opinion rather than advice.
I have two drives, for no better reason I guess than,when adding as at first a CD writer to the original CD player, it was the easy thing to do rather than rip out the original, and ultmately when the DVD writer came along out went the reader.
Belt an braces too.
However copying on the fly I never do, always copy to HDD and burn from there.