It will be a short one only on this specific issue – no picture or tables and such. More on the 7750M and 7770M will follow soon.
So, the 7730M has the same chip as the 7750M and 7770M only it has a DDR3 memory which cuts its memory bandwidth considerably. The performance, by early benchmarks and tests are on the Radeon 7690M and GT 555M level, but is also more prone to more memory bandwidth-intensive games probably. These games can be discovered by comparing other GPUs which differ only in their memory type/interface (DDR3 vs GDDR5) like the Radeon 7670M DDR3 vs Radeon 6750M comparisons.
Metro 2033 is one such case and I guess there will be a significant difference between the 7730M and the 7750M in this game, for example. However, comparing many other games (1, 2) and configurations we can see that the 7730M performance is between the 7690M and 640M performance but generally follows the 7690M performance, maybe a bit more. We’ll have to wait for more reviews with more cpus to see the picture fully.
Bottomline is, although the 7730M comes with superior raw performance, it’s limited by its memory bandwidth and in practice you’ll get something like the 7690M performance, sometimes OC’ed. The 7730M number (notebookcheck) confirm it – the 7730M is something like the 7690M performance-wise, sometimes faster and sometimes slower, but averagely the 7730M is equal or faster.
Compared to the GT640M it’s sometimes faster, but keep in mind that some of the numbers are the comparison of the GT 640M+I7-2637 vs 7730M+I7-3612QM and the I7-3612QM is clocked a bit higher (about 5-10% higher).
Radeon HD 7690M vs 7730M?
Performance-wise, I don’t there is much difference, but the 7730M is 28nm part and supposed to be more energy efficient. So, everything else considered, take the 7730M.
Radeon 7730M vs GT 640M?
GT 640M no doubt. Usually higher performance and it’s energy efficient too.