If you're only planning to play tf2, it makes no difference. Again, I have the same specs as the one you're looking at and I actually run tf2 on the integrated card because some weird setting caps fps at 30 on the nvidia and I don't bother trying to fix it. But if you might want to play games like Skyrim or Far Cry 3 you should definitely look around a bit more.
What laptop you're currently looking at? I did a shit ton of googling to find the best price/specs when I bought mine just a couple months ago so I may be able to help you out.