I did a re-read of all of The Wheel of Time just over a year ago, and I can't begin to tell how much more impressed I was than the first time I read it. I loved it, and am very sad the Robert Jordan didn't get to finish what he'd started. He was almost there - and a re-read showed just how close he was, even though reading it the first time, and having to wait for each new book to come out, seemed like he had lost his way. He hadn't. And i think this is where the series gets a lot of bad press - it could have been cut down a bit with all of the descriptions. But so could Malazan - that could definitely do with an editor!
As for Malazan, I've read the first 4 books and stopped about 10 years ago (I think). I just re-read the first 2 again. I really have to say, Erikson's writing is poor. He does a fantastic job of world building, but his writing, characterisation, etc. is really poor. Even his magic system is badly conceived and described - i don't think even he knows how it works properly. As for being too complex - i have no problems with that and only struggle to know what is going on when I can't understand what he's actually written. As for it being more adult - describing bits of body parts and sex scenes does make it a bit more adult, but does it make it a better read? I don't think so. Jordan was actually involved in war, and I find his battle scenes much more realistic and 'human' than Eriksons. I will probably re-read book 3 again, but if i don't REALLY enjoy it, I'll stop again. Too many other great books to read.
So, to compare both series - I haven't finished Malazan, so I really can't - although that in itself says a lot. I didn't finish it because I didn't enjoy it. But people do seem to put Malazan on a pedestal, and I disagree. I'm a fan of Wheel of Time, and I think some of the characters in it are very real in a lot of ways.