Maybe I can give you some insight, I was a dock master on B for years, and I'm also from the islands. Here is public dock low down:
B dock is the most popular because it is the most protected, closest to the bath house and home to the majority of PIB boating regulars...tis where Dock Trash was born. Here you'll find people who don't consider themselves tourists, and aren't thought much as tourist as they are there just as often if not more than many people who own cottages on the island.
A dock is the second most popular and most protected. A dock has it's own set of regulars but a smaller group. They try best to be up around the finger area. However the old outside wall there isn't the best place to be if the wind kicks up, its spring so NE winds are very common.
C dock is the least popular of the docks, infact I wouldn't tie boat up there if it was the last place to dock. Not worth it. It is the least protected because of the blue part. This is the dock where boats sustain heavy damage, and often. In fact it is the only dock I've seen boats basically sink at. I've seen a lot of boats with holes punched in the side when the wind kicks up so hard and throwing boats up side ways onto the posts. No joke. Infact one night I was working and C dock asked me to help save boats getting beat to death. A brand new 39 ft. Sea Ray, first day out, got crunched so bad, but it was too big for us to hold off the dock. The owner came down saw the damage and had a heart attack right there and died if front of all of us.
So what it boils down to, the more popular the dock the earlier you have to get there. Things have changed a bit, and due to gas prices many folks just aren't coming as often, making it a little easier to get a spot. But regulars know the good docks and they are the first to go. When I worked on B dock, you would have to be there no later than Thursday before Mem. Day, to be second or third out. Fri by noon full. The fourth and X-mas we would be full the week prior. It's all about how early you can be there, and people who want to be in those spots do what they gotta do to get them. Last year B dock changed their rules and you could bring your boat up and leave it unattended a couple of days to get a good spot for the weekend. I don't know if they are planning on doing it this year or not but it might be something to look into. You can call DeRivera Park, the parks owns B if didn't know. A and C are owned by the village.
I hope this helped, and I hope you have a fun summer enjoying your boat. I know I'm counting down the days till I can put in! But have to do some work on the out drive and air conditioner before that happens.