is 32nm dual core 2.66Ghz (Turbo 3.3Ghz) with GPU on the same package as CPU.i7-720QM Clarksfield
is 45nm quad core 1.6Ghz (Turbo 2.8Ghz). The i7-720QM get's its Intel HD Graphics on a separate part of the laptop chipset.
If you earn a living doing 3D design and analysis and
your applications support multi-core, multi-threaded CPUS it's probably worth your money to upgrade to the quad core. 4 cores, 8 threads vs 2 cores and 4 threads. There is also a chance the faster dual core CPU will be better suited to your software. Be sure to check that out.