Differences other than Grill and Engine?

[pongpap]

Exterior
Black Grill on 3.0 and Titanium Grill on 4.8
Fender flare if you have 20" wheel or bigger.
(If not then 3.0 & 4.8 has the same flat fender flare)
Window trim just like "kimg9582" said
Exhaust tip on 3.0 are round and 4.8 are oval shape.
Rear view camera (I think this is standard on 4.8)

Interior
Seat are different (head rest, and electric lumbar support)
Sport steering wheel on 4.8
Sport button on gear (4.8)
Stainless steel trim on gas and brake padels (4.8)
More speakers on 4.8 (Better sounds system)
Active steering is standard on 4.8
Heads Up Display (optionsl on 4.8)
Rear seat DVDs on 4.8
Air vent on door pillar on 4.8

That's all I can think of at the moment