The more I keep hearing about the 3DS XL, the better. I've been hearing from more sources that went hands on that the 3D effect is apparently better because of the larger screens, and I've heard that "ghost images" are also much less of an issue (I had this problem show up a good amount on my original 3DS, if a brightly colored object went up against a dark colored one [such as Mario's red and blue against something black or brown] then I'd get ghost images to the left and right of the bright colored object). I also noticed that the XL model might be more fingerprint resistant as well, and the edges look more rounded (so now if I play a more intense type of game, like a fighter, then the corners won't be jabbing me).
I also just realized another reason why the XL is getting a CPP instead of just having a second pad added on: the extra shoulder buttons. Remember, the CPP also adds two extra shoulder buttons to the system, which has proven useful in games such as Metal Gear Solid 3D (allowing the controls to work more like the PS2 original). Still, in the end it's not like the CPP is something you need to have, but hey it's still a useful option for those that want it (like me, I already got a CPP for my original 3DS, so I'll be getting one for my XL too).