The Radion headline spec:
ASUS G Series G73JH-X1 NoteBook Intel Core i7 720QM(1.60GHz) 17.3" 8GB Memory 500GB HDD 7200rpm DVD Super Multi ATI Mobility Radeon HD 5870
The GeForce headline spec:
TOSHIBA Qosmio X505-Q875 NoteBook Intel Core i7 720QM(1.60GHz) 18.4" 6GB Memory DDR3 1066 320GB HDD 7200rpm BD Combo NVIDIA GeForce GTS 360M
You're not comparing like with like. The Asus has more memory and a larger hard-drive than the Toshiba so that might point to the graphics being lower spec. However, other components might well also account for the difference in price.
Both graphics cards have the same memory and the same display resolution so I would say that they're are much the same. Check out some reviews and performance stats of the two cards and see if they make the choice any easier.