The Monster Double Barrels are beautiful speakers with very nice disconnects, they will sound great around the boat and OK on the water.
The WetSounds Pro-80s are probably the most compact speaker for to get good sound to the rider. They are very light, very efficient, and very high quality.
Both are great companies that stand behind their products. Both are run by real wakeboarders that understand the needs.
If I were in your shoes I would base my decision on how I intend to use the system. If the towers speakers are intended to provide music to the rider then I would go with the WetSounds. If I wanted the speakers to fill the boat with sound with the rider being the secondary target I would go with the Monsters.