I've been to most of the pool parties on the strip and Encore Beach Club is my favorite. They beach club is big and they have multiple pools so there's always room in the pool when I'm there. The drinks are pretty outrageously priced, but I usually go because they have great headliner DJs.
My one complaint about this venue is that the floors are VERY slippery when wet...which is why they constantly have staff members sweeping the water away. I've seen at least 20 people in my visits to the beach club slip and its not pretty. So my suggestion would be to ALWAYS wear slippers when going to and from the bar, bathroom, tables or wherever you're headed.