FA is like a HUGE, MASSIVE city with millions of inhabitants.
Weasyl is like a little village or something alike, just with a couple of hundred of inhabitants.
Well, now I don't know how many use Weasyl and FA, but that's how I see the both.
Just because.
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Sleet the Fox
Weasyl is quality, FA is quantity. Weasyl is a better site but it's much more vacant.