As I mentioned, in OSX benchmarks shows that it is faster. Could part of it be CPU? possibly. The OPENGL bench in cinebench seems to show the 6490 outperforming the 330m though. Whatever the case, as I mentioned, the 6490 will always be paired with the quad core in these MBP's and the 330m with dual cores so the 6490 still is the better buy, especially if gfx can be considered negligible difference.
Cinebench R10 OpenGL is not a reliable test for the performance of the GPU.
You can see how badly Cinebench R10 OpenGL is influenced by the CPU of the following scores.
An Intel HD3000 better than the ATI 5730m and the 335m? A 310m faster than a 335m?
Core i5-2520M/HD 3000 ********** 5757
Core i7-2720QM/HD 3000 ********* 5378
Asus N61, Radeon HD 5730 ******** 4890
Acer Aspire 5943G, Radeon HD 5650 ******** 4822
Samsung QX310, GeForce GT310M ******** 4625
Samsung SF310, GeForce GT310M ******** 4619
Asus NX90, GeForce GT335M ******** 4537
Samsung NP900X3A, HD 3000 ******* 4024
Games show that the ATI 6490m is not better than the 330m which is highly dependent on GPU power, despite being gimped with a weaker CPU.
In the year 2011, a low end 6490m doesn't belong in a $1800 laptop.