Never. Bigger is always better, at least thats what she said.
Seriously, I really don't understand prefering the smaller 3ds over the XL. Yes, I've read the reasons why some think the smaller 3ds is better, but in a few of those areas, those reasons really don't seem legit.
First, the XL is too big. Yes, the XL is bigger, but overall, not that much bigger. I keep my XL in my front pocket while working, I even keep it in the little blue cloth pouch from Club Nintendo and I didn't notice the XL being any less comfortable than the regular model.
Second, the XL's screens are so big that the image is all blown up and it looks all blurry, pixelly, ect. A while back when I owned both the regular and the XL(I still owned the regular 3ds cause I had not sold it yet), I was at my mom's and some kids that she watched owned 3dses and had their games with them. I compared SM3DL, LM and one other game that is escaping me right now, side by side on both units. I'm being 100% honest, I saw no difference in the quality between the units. If anything, I could notice that the jaggies were a bit more pronounced on the XL, but that doesn't mean jaggies didn't show up on the reg. 3ds. Same jaggies, just smaller. Without saying anything, I asked my mom and a couple of the parents that were there at the time to check out both units and tell me which screens look the best. Other than the size difference, they all thought they looked exactly the same. Afterwards, I told them some think the XL's visuals are blurrier, ect, ect. They checked out the games again, same verdict.
I'm not trying to change anyones mind. If you prefer the smaller 3ds, thats all that matters. Yes, I guess someone who has a small body frame might find the XL too big in their pockets, esp if they wear jeans, ect that are not loose fitting. I really feel the picture quality on the XL being way too blurry, ect., is all in your heads. I didn't want to state it that way, but I couldn't think of the word I was looking for. I feel that those who believe the picture quality on the XL to be inferior, are seeing something different, or at least truly thinking that they are, but I'm not buying it. Other than the jaggies being a bit more pronounced, I see no difference. I stand by that 100% so much, that I bet my life and my loved ones life on it. I have perfect 20/20 vision, so its not like I have bad eyesight.