The two GPU's you have listed use completely different architecture,
For example: A stream processor from a GT440 is not equal to a stream processor from a HD6450.
The only effect way to compare GPU's is to look at reviews.
Have a look at this HD6450 review: http://www.tomshardware.com/reviews/radeon-hd-6450-caicos-blu-ray-3d,2920.html
As you can see even the GT430 is faster than the HD6450 so we can safely assume the GT440 will be even faster still.