I quite enjoy doing copywork.
And I love studying masterpieces (whether it be music, text, art, or source code), and figuring out what makes them so masterful.
Copywork and master studies are distinct acts of learning. They should not be conflated. I distinguish them so:
Copywork relates to the act of the copying itself. As you copy, you will be forced to recreate and absorb the patterns, structures and styles used by a skilled master. What matters in copywork: that you copy the opus entirely, or large chunks of it. Yes, one may learn and appreciate much from copywork; but I argue that such is incidental to the act of copying itself.
In contrast, nothing is incidental about master studies. A true master study is a deliberate effort at conscious, exacting analysis: of the limitations, tradeoffs, options and decisions an artist took when he created his masterpiece. You analyze the final work, evaluate it, critique it (if possible), and learn more about its technical/functional basis and other applications; you can even attempt to emulate the skill/style required, and adapt it as part of your own repertoire.
Master studies are about deconstruction. A proper master study is extensive; after all, a masterpiece (or the finesse of it) might have first required the master to hone his skill over years, decades or a lifetime of experience. If so, what leads you to believe that you can undertake it all in one sitting?
So a master study is often done in chunks. Nothing actually needs to be copied whole when you're doing master studies; you study from smaller cuts of the main work, tie each dissected knowledge back together, and study the pieces as well as the final fit.
Copywork can be for drilling, unlike master studies. When copying, you do not need to be conscious of all technical details; sometimes all you want is to achieve automaticity, and flow of replication. (After all, you can never gain motor familiarity from just looking or thinking of doing something.)
Think of musicians who practice a certain song until it becomes muscle memory; no amount of piano study will be the same as piano practice.
Copywork is tied to the medium, but not master studies. For instance, I cannot copy a piece of written text to improve my skill with a paintbrush. And I cannot learn to sculpt stone by re-transcribing a music score.
However, when I'm doing master studies, I can apply my analysis and study to other things: e.g. I can study saxophone licks, and transfer (or 'transpose') the melodies or harmonic analysis to the guitar; I can study a painter's brushing techniques, and apply it to how I wield my chisel or how I oil my knives; I can study a writer's concise programming style, and apply it to how I refactor my legal pleadings for maximum clarity.
One can engage in copywork without doing master studies, or vice versa. But I think you benefit most by doing both.
In the end, I don't see either learning technique as better; what matters is my realization that copywork and master studies are distinct tools, either of which can be opted for when met with gaps in my skill/knowledge.
Modern society likes to knock on copywork, as if one's 'conceptual understanding' alone can be superior to rote drilling.
If you've any doubts about the efficacy of copywork, consider what Benjamin Franklin did throughout his life:
...As part of his self-improvement course, Franklin read the essays, took brief notes, and laid them aside for a few days. Then he tried to recreate the essay in his own words, after which he compared his composition to the original. Sometimes he would jumble up the notes he took, so that he would have to figure out on his own the best order to build the essay's argument.
He turned some of the essays into poetry, which helped him (so he thought) expand his vocabulary by forcing him to search for words that had similar meanings but different rhythms and sounds. These, too, he turned back into essays after a few days, comparing them to see where he had diverged from the original. When he found his own version wanting, he would correct it. "But I sometimes had the pleasure of fancying that in certain particulars of small import I had been lucky enough to improve the method or the language, and this encouraged me to think that I might possibly in time come to be a tolerable English writer, of which I was extremely ambitious."
...And see where Franklin's copying efforts got him to.