Both chips can be Kepler or Fermi (thanks a buttload for the confusion on parts naming, NVidia), but the likelihood is that both will be the current standard of Kepler with 96 Cuda cores for the GT630M and 384 Cuda cores for the GT640M.
I think you have the right idea, go with the GT640M.
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...
I'm sorry, I misunderstood you, I thought you said you were going to keep this new laptop for 3 to 5 years. You're right, the i3 is definitely the way to go. Also, I can see where "stylish looks" beats USB 3.0 and better video, hands-down!
The Dell monitor has a more efficient (less power required) backlighting system WLED, than the Sony, it also has a better graphics processor than the Sony (HD 7670M vs HD 7650M) and the Dell also has three USB3.0 ports, while the Sony has only two USB2.0 ports. The difference in USB 3.0 vs USB...
You're asking conflicting questions. Do you want "cheap" or "best configured"?
You can go here and decide what works best for you. http://www.dell.com/us/p/alienware-m17x-r4/pd
it's $1500 at it's "cheapest", but $4000 at it's "best configured"...
Try this. Your Toshiba should have a built-in recovery partition assuming you have never wiped and reinstalled in the past.
https://www.csd.toshiba.com/cgi-bin/tais/support/jsp/bulletinDetail.jsp?soid=2737864&pf=true
http://www.geekpolice.net/t18281-toshiba-recovery-partition-hotkey-instructions
Dell offers better support (really!) but you'll pay for it.
The two machines are virtually identical in choice of procs, drives etc.. The only real difference is in the available GPU. Asus offers a 2GB nvidia GPU (GT635M) and Dell offers a 1GB AMD (HD7570M) product.