Pannier is pronounced PAN-yer or PAN-ee-yer. I prefer the latter.
Both petticoats and panniers DO the same thing, essentially. They both "poof" the skirt/dress.
Petticoats are underskirts. In lolita fashion, I suppose it is preferred to have them be crinoline, so as to make them poofy-er (sp? Is that even a word?). I'm pretty sure any underskirt is technically a petticoat, though.

(My petticoat; not a particularly great one but it serves it's purpose...)
Panniers are... weird. To me, anyway. They are more of a basket+cloth arrangement. I don't know anybody that wears "full" panniers but I've seen the sort of... "half" panniers. They make you look more wide than poofy, I think.
