Google Maps is a hundred times better (and on the Android is even better).
Apple Maps has many mistakes and inaccuracies, hasn't got Street View which I miss, has inferior satellite imagery, often incomplete maps (when looking at smaller cities and towns). The 3D cities are a gimmick and only look good from a distance (at least on my 4S) and sometimes the animations are really choppy.
Don't get me wrong, the Maps are fine, however they feel like a downgrade, and considering how much experience Google has with maps they will most likely always be ahead of the game.
EDIT: Oh, and I forgot to mention that it crashed at least twice on me when switching between modes.