The o2DS is the normal sized version. I know, it's not the same thing, but it's not just about differentiating between sizes. It's also an easy way for people to tell that it's a larger sized console than normal without looking at dimensions or pictures. Dimensions don't tell the whole story, and pictures can be misleading.
I actually played in one and with my E.T. fingers (lol) it's actually felt comfortable than I expected XD
the console itself was nice to use but I don't liked the way it was lauched, like
NoA: hey, Iwata must be sleeping now
(he was alive that time...), Let's annouce it now!
Iwata in the morning seeing the notice: NANISORE!?
(one joke some friends told about haha )
I mean, the developers of Zelda ALBW don't even knew it was going to me released, and it had to change an important plaling feature of the game so it could be playable in 2D... in other words, a downgrade of the console, what sounds kinda sad, like that " wii family edition" (without GC compatibility) or the Wii mini, that where exclusively western nintendo models, even the o2DS almost haven't went to japan!
(A good thing is that theoretically it made the console more accessible... not a reality here in brazil that it still coust more than an oDS because it's "the newer model than it" =3=)
Second is that the o2DS is a peculiar 3DS, it isn't an 3DS and it's isn't a even a DS! (Another joke, because the thing about it having one a large screen actually hahh) at least the n2DS is a DS now