On top of all the obvious aesthetic, ergonomic and screen-wise improvements, there are a bevy of small additions and changes that differentiate the 3DS XL.
The system's tactile feedback has been improved all around. For example, the 3D slider on the top screen—the one that lets you crank the 3D effect from zero to eyes-bleeding and back again—now clicks at the bottom. The "select," "home" and "start" buttons now have clear edges, eliminating the headache caused by the original buttons' smooth, contiguous surfaces. The top screen even has a new locking position at about 45 degrees, perfect for watching or playing certain games while the system rests on a table.
Best of all perhaps is the stylus's return to where it should be: on the side, easily accessible whenever you need it. That alone improves any 3DS experience markedly.