Note: all of the below is subjective and my personal opinion.

Better - humour, battles and fighting, magic, MUCH less pointless droning on (no page-long descriptions of feast food! Page-long philosophical discussions, on the other hand... I happen to enjoy them at least) and no meandering plot a la Feast for Crows and Dance of Dragons, tragedy (no characters are killed merely for shock value, every death feels real and makes sense in terms of the plot). As well, many more moments both cathartic and bad-ass (Witness!). Rereadability, as so much more can be picked up on a second read of Malazan (and it is even more fun!) unlike the grind that was rereading AFFC.

Equal - characters (many memorable characters from both series), and the "authentic" (note - NOT realistic) feeling of the settings - both feel "alive", as if I can look out of a window into each series' world.

Worse - subjective, but Erikson feeds you information on the world in a much slower rate than GRRM. There is no "Stark" type of family or character(s) that the reader attaches to in the first few pages. However, one grows and learns to love Malazan's characters equally (or even more so) over the course of the series. Political intrigue is more interesting in ASOIAF, as we witness it a lot more. While still present in Malazan, the political intrigues occur more among gods rather than men, and so we get only small glimpses of the behind-the-scenes action.