I just came back from a second visit to Washington State, this time teaching at the Pacific Northwest Writers Association conference. Last month I presented at Cascade Writers Conference in Tacoma. Same state, but opposite types of conferences.
Cascade Writers was small, about thirty people. It changes a little over time in part because it's newer, but mostly because of the size. The organizing committee is also small, and comes down to the work of a few people.
PNWA is big, has been around for 60+ years, and has a large number of volunteers. It was in a nicer hotel, with more name authors and agents, and was also more expensive. With so many editors and agents, however, you have a much greater chance of talking to multiple people about your work in progress than at Cascade Writers. There were a lot of smart, on-the-cusp aspiring writers, too, and someone at the conference is almost guarantee to join the ranks over the professionals year in and year out.
On the other hand, with hundreds of attendees, you would never know the majority of the people at the conference, and if you're an introvert, you could feel like you're bouncing through the crowds, frustrated that everyone else seems to be having a good time, while you're lost and lonely. At a smaller conference, you'll meet everyone, people will notice if you need to be included, and by the end of the conference will feel like you're a part of a tight community.
I sometimes get asked what kind of conference I prefer. There is no good answer to that. I had a great experience at both (chalk one up to the generally friendly vibe of the Pacific Northwest), and enjoy the ability to vary my routine from one conference to the next. I might have a class of eight in one event, and 80 in the next. They are invigorating in different ways.
One preference I do have is to have a conference filled with aspiring professionals working at the high intermediate stage. That's where I feel I can contribute the most, and where you (assuming you're savvy enough to hunt down this blog) will probably get the most benefit, too. I have been to a conference or two over the years where it's clear that the guests are hobbyists, there primarily for the social reasons. There's nothing wrong with that, if you're a hobbyist. Since you are not, you should avoid spending your time and money at events that aren't filled with ambitious, hard working people like yourself.