well the geforce gt 550 would run better then the geforce gt 520 so I would go with the seconded option still. You can read about the video cards in the laptop on these two articles describing there capabilities and uses and so on.
NVIDIA GeForce GT 520M - Notebookcheck.net Tech
NVIDIA GeForce GT 555M - Notebookcheck.net Tech
Anyways the one with the gt 550 would run games better then the one with gt 520
GEFORCE GT 550 Description
The performance of the GT 555M is highly dependent on the version of the card (see above). The 3DMark 06 performance, for example, ranges from 8857 points (Lenovo Ideapad Y570) to 13000 points (MSI GX780R). 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 (see below).
Geforce GT 520 description
As an entry level card, the GT 520M has to compete against the Intel HD Graphics 3000
in the current Sandy Bridge processors. In our tests, the card was only slightly faster, but the better driver support did make a difference. However, demanding games like Battlefield 3 or The Witcher 2 are not playable. Other modern games only run in low details, and therefore gamers wont be pleased with the performance. Low demanding games like Fifa 12, however, are playable with high detail settings.
So if your going to play stuff like GTA IV i highly recommend the 2nd laptop