Personally, I prefer the XL. The buttons and D-pad on the normal 3DS feel mushy and tend to squeak (and, quite frankly, it's a bit of a stretch to call the Start, Select, and Home buttons...). The XL is also better for backwards-compatibility - on both systems, the upscaling from the DS's resolution to the 3DS's resolution is rather poor and makes text blurry, but holding Start when selecting the DS game (or DSiWare) overrides that and puts the DS game in its original resolution, with black bars around the screen. On the normal 3DS, this is extremely small - smaller than the original DS's screen - while on the XL, the DS game is about the size of the DS Lite's screen. The XL also has slightly better battery life (3.5-6 hours vs. 3-5), and the 3D slider has a definite off position rather than just automatically switching off on the lowest setting.
Of course, the XL's screen does look slightly more pixelated because of the increased size, and it is rather bulky. It also costs $30 more, and doesn't have a charging cradle (though contrary to popular belief, it does come with a charging cable - at least, outside of Europe). I think the benefits outway the downsides, but really you're not going to know until you try them out.
