I use smooth-on and versamid and they both do a fine job. Smooth-on will cure at lower temps and versamid requires an oven, it will not cure at room temperature. Like Kenny said, it is thinner and will soak into lams and leave dry spots, so use plenty. One advantage to versamid is the longer working time, even in the summer you dont have to hurry with the glue up. Another advantage is being able to spread it with a roller.
I think smooth-on is more versatile and that is what I use the most of, but either will work.