One thing (an important thing) to consider when choosing an excavation to join is the extra-curricular activities. By that I mean the evening lectures and the afternoon or weekend tours. Digging in the dirt is nice, but your experience will be greatly enhanced if you can learn about your site and travel around the area. Having said that, and having looked at the schedule at Gath this season, I would certainly recommend choosing Gath for your excavation next year. Check the schedule out at the Gath blog. A tip to other excavations interested in boosting their number of volunteers for future seasons: put your extra-curricular schedule online. And start a dig blog.
Yigael Yadin lecturing at Megiddo excavation, 1967from forthcoming photo collection of David Bivin