I disagree, I generally find Melbourne CBD to be dirtier and less taken care of than Sydney, my cousin first pointed it out last time we were in Melbourne and I took note, the place is not clean at all.Sydney CBD is definitely dirtier
Especially when it comes to old heritage listed buildings, Melbourne does nothing with them in the way of keeping them clean were as in Sydney the older sandstone etc buildings are fairly regularly cleaned, like QVB and Central etc so that they don't look like they are falling into disrepair.