confused

[biggy]

Hi all,
looking to get a dell xps15 and have narrowed it down to two options.

The 1st option has Core™ i5-560M Processor (2.66 GHz,3M) with a 1GB NVIDIA® GeForce® GT 420M Graphics Card

The 2nd option has Core™ i7 Processor 740QM (1.73 Ghz, 6MB, 4C) with a 2GB NVIDIA® GeForce® GT 435M Graphics Card

So 2 questions, which combination is best for gaming,surfing,watching movies and multitasking?

Also why is the i7 only 1.73 Ghz and the i5 2.66 Ghz ? am I wrong in assuming the i7 should be faster?

cheers

 

[biggy]

Thanks lads that pretty much explains everything.
Oh what is optimus-enabled and IGP?