I love Miéville (well, his good stuff; his B roll not so much). But he's always going to be below Gibson on my ranking because Miéville's worlds and characters, while rich and innovative and unique and fascinating and and ... all seem so deeply _hopeless_ to me.
It's ironic. Gibson writes about hypercapitalist dystopias (present or future), often starring burnouts and addicts, but manages, through all the grit and suffering, to often hint that things still tend towards hope--even if only in small, human ways--despite the overly cynical tone of the world: the AI ascendant, heroes tropily settled down. Miéville, on the other hand, writes of worlds packed with magic and intrigue and hypertrophic growth, but often ends his plots (deliberately, I think) on a hopeless, stagnant note.
There are exceptions to both trends in each author's bibliography, to be sure, but it's a really pronounced juxtaposition (at least for me).
Whenever I start a new book, I have the impression that it is written in subtle different language. It takes my brain a little while to catch on.
China Miéville has that as well in a different manner.
Gibson seems to me to be an author who thinks about every single word.
His texture is unique.
Some his later books have some slow passages.