Memory bandwidth is only important up to a certain point for general stuff, but for memory intensive stuff like Anti Aliasing, you need more bandwidth to be able to feed the GPU fast enough. It would be much harder to test with a card like a 5450 as AA will crush its frame rates just due to the extra computations needed and not due to the need for additional memory bandwidth.
For a card that weak, the core clock is by far the more limiting clock speed, lower end cards tend to have way more memory and way more memory bandwidth than they can use to start with so boosting the memory clock wont do you much good if any.