I bought a 3DS XL for the wife, and a regular 3DS for a friend. After spending some time with both of them myself i have to say i much prefer the XL. Obviously, the bigger screens are great and make certain things a lot more convenient. For example, text in games like Zelda: A Link Between Worlds is much easier to read on the XL. To my eyes, the XL's 3D also seems a lot better looking and much easier on the eyes. This is probably a direct result of the bigger screen, and the fact that it's easier to find that "sweet spot" for the 3D to really pop. In regards to it's physical dimensions and shape, the XL is more comfortable to hold for long periods of time and is surprisingly light for a relatively large device. I also notice a greatly improved battery life.
So far, that's about all i can give you. Hope it helps!