I think a big consideration is whether you want a legal or symbolic wedding at your destination. Since my fiance and I actually wanted to get legally married in front of our friends & family on a tropical beach, we had to find somewhere where it was easy to do so. We found St. Lucia and Jamaica to be the easiest places to legally get married (no translation of documents or blood tests). Since Jamaica was the most cost effective for everyone to attend, we chose Jamaica.
Oh and I highly recommend a travel agent! Mine has helped a lot and took some stress off me