Should you advertise in big places or small places?

Say you had a social leather website for guys into leather, like a leather myspace, and you want to promote it at leather runs to spread the word on it.

Would you be better off advertising your site in smaller places that dont have much attendance but theres also less competition for you?
or would you promote it at the BIG events, like MAL or IML where theres way more people who see your ad, but also way more competition of advertisers?

if the big places and smaller places you are thinking of are both pretty much the same niche, well, the bigger places have lots more traffic. otherwise you're comparing apples to toilet seats because advertising only to people who would be interested would be the thing i was most concerned with, and two other things - i would advertise only when my site had the overall signup ratio i wanted and i would make sure that my banner was kickass with a tested clickthrough ratio before i paid to place it anywhere.

Thanks for the advice Basschick.
Im going to try advertising in a small leather weekend event just to see what happens, and if the response is good Ill do bigger ones.