The Y570 has a 96 cores 753MHz (GF108), 128Bit GDDR5, GT555M.For all intents and purposes, the GT 555M in the Lenovo is therefore essentially a fast GeForce 550M. The average GT 555M (with 144 shaders) is positioned in the lower high end class and enables users to play demanding games in high settings at 1366x768. Only Metro 2033 had to be played in lower settings during our benchmark tests
Whereas Y480 has a GT 640M LE due to a clock speed of just 500 MHz, the gaming performance of the GeForce GT 640M LE should be about 20 percent below the 640M. This would be the same level as the GT 635M or the GT 555M. The performance is exceptionally good in shader-heavy DirectX 11 games and benchmarks. However, the 128-Bit memory interface can be a bottleneck if DDR3 graphics memory is used. Demanding games of 2011 like Battlefield 3 will be playable in 1366x768 and medium settings.There's also another part you might want to be aware of, the GeForce GT 640M LE, because it's 1.) not as powerful as a regular GT 640M, and also 2.) comes in two different variations. One is a 28nm Kepler part, the other a 40nm Fermi, and there's no good way to distinguish between.
Regarding the processors, the i5-3210m has the same clock speed as the "Sandy Bridge" i5-2450m. However, it provides about a 5% - 6% increase in performance on average over the i5-2450m which makes the i5-3210m a slightly more powerful CPU.
Ivy Bridge CPUs consumes a little less power than Sandy Bridge CPUs so battery life should be slightly better assuming both laptops have the same battery.
Ivy Bridge CPUs comes with the better performing Intel HD 4000 graphic core compared to the Intel HD 3000 graphic core found in Sandy Bridge CPUs. If you are buying a laptop with a nVidia or AMD graphic card, then this is more or less a moot point.
So if you look at various FPSs of the games GT555M will come out on top.So for purely gaming purposes I would suggest the Y570 due to the graphics card and the bigger screen.