Mona just doesn't do it for me like
Nona does. I think it's a color thing: 'n' is very orange to me, and having two in one name, in such close proximity, makes it much more vivid to me. 'M' is more of a pink-purple.
In that vein, like
Nina a lot, too, but my boyfriend doesn't at all...plus I kind of like
Nona (vs.
Nina) because it doesn't have quite the same amount of "mainstream namenerd" appeal.