BF2S Forums Laptop Intel Core i7 CPU Comparison

i7 740QM is more powerful because it's a quad core (4 cores, 8 threads)
it also has 21 GB/s max memory bandwidth and 45 nm lithography and
6 MB cache. It supports DDR3 1066/1333 memory speed, and has 774 million die transistors.

i7 620M is a dual core (2 cores with 4 threads). It has new AES instructions,
32 nm lithography, integrated graphics and has 382 million die transistors.

In my opinion the 620M might be enough. If you want the most powerful processor of those two, the 740QM is the strongest.

The other specifications of the two processors is here: Compare Intel® Products