Looks like face plates don't beat screen size.
Thanks to sales figures published by Famitsu, we can now see that the vast majority of Japanese gamers have picked screen size over face plates.
Over the course of the systems launch weekend, the standard sized New 3DS sold 61,151 units while the larger New 3DS LL managed to sell a whopping 172,332 units. That's nearly three times the sales of the standard New 3DS.
When Nintendo announced the New 3DS and New 3DS LL, it was revealed that only the New 3DS would feature interchangeable face plates. The New 3DS also features a redesigned form factor (similar to the original 3DS XL) and a larger screen than the original 3DS. These things combined made many assume that the New 3DS would outsell its larger counterpart. It would seem however that in this case, it really is the size that matters.