Canelo's defense is multi-dimensional. He parrys very well, he uses excellent head movement, he can effectively use the shoulder roll, he always has a tight guard, he never gets hit as flush as GGG, and uses great waist movement against the ropes.
Canelo slips and dodges better but GGG has better parrying. In terms of guard I give the edge to Canelo since it comes natural with being a counter puncher. However GGG uses his guard and the shoulder roll about as effectively as you can being a pressure fighter.
Golovkin actually when he is fighting to be defensively responsible has better defense than Canelo. When he's working behind his ramrod jab, keeping opponents at range, and parrying down their strikes there aren't a lot of fighters that can get around that. Canelo has never displayed the type of skills Golovkin has in his fight vs Lemieux. That being said, that isn't what Golovkin normally does. He also has moments like in the Willie Monroe where after he knocked Monroe down he just...stopped caring about his defense all together. He isn't getting hit on purpose exactly as much as it seems that he doesn't care if he gets hit or not. They are both different fighters though. Canelo has better upperbody movement, but his feet are very slow. Golovkin is not what people call "slick" in boxing at all, but his footwork is very good and part of the reason his movement is the way it is is because he is always trying to position himself to deliver a power punch which his opponents are weary of so they often throw less than they normally would in fear of getting caught.
Golovkins footwork seems to be solely focused on balance. With perfect balance you get a lot of benefits that we see in Golovkins game. His ability to always be in a position to throw power shots, his ability to take hard shots, and his ability to keep the proper distance and cut off the ring. In a way, you could call perfect balance great defense.
Golovkin gets his head knocked around like a bobble head a few times in each fight against sub par competition. Canelo hardly ever gets hit cleanly with his tight guard, head, and waist movement. How can you watch this and watch Golovkin fight and get hit clean in almost every fight and say GGG has better defense. You have to be wearing some thick fan boy goggles. This content is protected
a couple of things confound a direct comparison (ie, ranking one over the other) workrate GGG's workrate (punches thrown per round) is probably close to twice what Canelo's is and my guess is that GGG's landed:thrown ratio is equal to Canelo's if not higher such a big difference in workrate means they prioritize pure defense quite differently style counter-puncher versus a pressure fighter--again, defense has a different priority and lastly, while it's common to talk about defensive skills versus offensive skills, i have never thought that this distinction is valid in boxing; it is in the NFL, NBA, or baseball--ie, at any given time, a team is either on offense or defense but boxing is different--fighters are simultaneously on offense and defense. For instance, GGG's jack-hammer jab is clearly as much of an offenseive weapon as a defensive weapon (a fair number of boxing commentators say that it was GGG's jab that so effectively throttled Lemieux's offense). same thing with balance and position (and the footwork necessary to sustain it, versus footwork to move around the ring). GGG's balance and position are the foundation for both his power and his iron whiskers. When he throws, his chin is tucked and his body is deliberately angled so any punch to his melon causes it to rotate as little as possible (punches that generate sharp torque to the skull are what cause knockdowns, likely everyone here already knows).