While the i5-3210M has turboboost to 3.1GHz, it wont make up for the difference in GPU capability between the GT630M and the GT640M. But then, you haven't provided sufficient information (laptop model numbers) since the OEM variations in either of those GPUs can be crippling or enabling in terms of performance. For example, there are variants of the GT630M with 192 cuda cores and GT640M with 144 cuda cores. Not common, but you need to be certain with what your prospective laptop will be equipped. There is also the matter of DDR3 vs GDDR5 memory. Both GPUs can be coupled with either and, of course, you will want the GDDR5 RAM, if available, on the laptop.
So, you have more research to do. Find out (from the ACER website) which RAM is on them and which GPU variant is being used. You specifically need to know whether the GT6x0M is the Kepler or Fermi variant as both GPUs could be either.