Canelo would win
Golovkin.
GGG has not been really tested at 160 while Canelo is sort of overrated himself at 154. This could be a breakout fight for both. Both could somewhat box and definitely punch. Size and weight would not be far apart at fight time. GGG would have the edge in power but Canelo has the advantage in experience in fighting at higher level. Technique and style I would also give to GGG. But he has to impose those as successfully as he had against lesser foes on Canelo which would not be easy given Canelo's comparative versatility and experience.And with Canelo fighting for the first time at a weight he is well at home and comfortable with without any mental reservations who knows how much better he can perform inside the ring?
GGG may be tested like he has never been before and it may or may not expose his limitations.
It's a toss up for me.
If Canelo is lured into a "toe to toe" battle 7th is the farthest he can go IMO. He's sloppy in his defense. With Canelo's immovable head,GGG's power punches would feast like flies on Canelo's face.
Cotto's brother is the dude who hurt Canelo badly and almost knocked him through the ropes.
Canelo vs GGG is a great fight. I think GGG would take Canelo out, and I'm skeptical whether his people will let Canelo fight Golvokin, but Canelo insisted on fighting Lara so that at least shows he's not scared of taking a challenge.
I think Golovkin stops Canelo in the 8-12 range.
With the relation between Oscar and Arum starting to get more friendly the liklihool of this fight increases.
Canelo can barely make 155 any more and will be quite a bit 160 pounder, very similar in size to GGG.
I think Canelo will get stopped in the championship rounds. GGG has a chin of iron and will keep on coming, whereas Canelo has shown stamina problems, poor decision making and a little bit of a shaky chin. Not totally sure what fight it was but he was wobbled quite badly by either Hatton or Cotto's brother.
GGG TKO R11