I actually prefer SeatExpert. ^
I've been let down by SeatGuru lately, they don't even have the layout for Singapore Airlines' 777-200ER even though this plane flies to a number or European destinations, also Sydney, etc.
Also for the A380, both sites have inaccurate information about row 80 DEFG. Only the armrest between seats E and F is immovable, the ones between D and E as well as F and G are fine. Also, people don't congregate in front of those seats because there isn't enough room.