The N10j has two graphic cards, an igma950 for battery-saving and the 105M(or 9300gs) for gaming. Since the Ion is an integrated card, when the 105M is a dedicated one, the Asus is better for gaming, and also with the swichable graphics can provide more battery life. The n280 can do the same with overclocking, but you can also overclock the 105M. If the price is not deciding factor, I'd defeneetly go with the Asus. Also please note when considering a gaming netbook, while the N10j is the strongest gaming netbook on the market, it is still rather weak for hardcore gamers, most of the time you will face CPU-limit, and will stuck to medium to low settings.
N10Jc @ 2.0GHz - WinXP/7 - Resolume 2.41 - Behringer BCR2000 - Pocket VJ
What's better than a powerfull small portable device? An even smaller powerfull portable device! I'm the owner of a brand new Nokia 5800 XM!