Lenovo Y500 vs Y510p, Need some advice

Hey guys, first time posting here.

Anyways, like the title suggests, I plan to get the Lenovo Y500 as my next laptop, mostly for gaming, and a good all rounder.
So the specs are as the following.

Lenovo Y500:

Intel® Core™ i7 Processor 3630QM (2.4GHz up to 3.4GHz, 6MB Cache)
Windows 8
15.6'' Full HD WLED
8GB DDR3 1600Mhz x 1pcs
1TB (5400rpm)
Nvidia GT750M 2GB GDDR5 onboard + Nvidia GT750M 2GB GDDR5(Removable GN37 SLI adapter) (Hotswappable)


Lenovo Y510p:

Intel® Core™ i7-4700 (3.4 GHz, 8MB Cache) Haswell
Windows 8
15.6'' FullHD WLED
8GB DDR3 1600Mhz x 1pcs
1TB
Nvidia GT750M 2G DDR5 + Nvidia GT750M 2G DDR5 *(Hotswappable)

So the biggest difference here is the Y500 uses a 3'rd generation i7 processor (Ivy Bridge), while the Y510p uses the latest, 4'th gen i7 (Hasswell) processor.
I wanted to know, would there really be a big difference in performance? Is the Y510p worth the price? Also, is the Y510p have been officially released in Malaysia? Or are the models sold here are grey market (US) models?