What to choose? GDDR3 or GDDR5 Memory?

I know a GDDR5 memory is usually faster than GDDR3, it improves memory bandwidth.

BUT

Does GDDR3 & GDDR5 Memory have anything to do with the pixel/texture units?
IMO, a higher pixel/texture fillrate with GDDR3 would out perform a lower fillrate equipped with GDDR5, am I right?

=>Example: A 7730M GDDR3 is better than 6770M GDDR5 in benchmarks.

I think,
Pixel fillrate used for - render pixels (resolution & anti-alising)
Texture fillrate used for - rendering textures (anisotropic filtering, etc)

& tell me which has better performance in games, HD 7730 or GT 640 both GDDR3?
Suggest any recommended laptops with similar GPUs.


PS: I am not comparing specs for AMD vs. NVIDIA or vice versa, because they seems to have different architectures, I only check relative benchmarks.

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Lenovo Y560 Laptop

Windows 8 Pro 64bit
Core i5-460m
Radeon HD 5730m + IntelHD 1000
4GB DDR3-1333MHz