To add to what Richard said (especially that they are just cool!) my observation is that when a grow bed drains using a siphon the water is quickly sucked through the bed, which has to be drawing a lot more oxygen to the root zone than the water just slowly meandering out by just a drain. Also I oxygenate my tanks in part using a diverting aeration system off the water-in fitting (in other words about 1/2 the water goes up to the grow bed, about 1/2 goes back to the fish tank to oxygenate it). It is best to have that oxygenation system running all the time, which you can do with a siphon system.
Downside - they are fussy! As solids build up in your pipes and water pressure changes they are reputed to be prone to failure.
You will also ensure a more even distribution of water and therefore nutrients to the plants since the water will rise evenly from the bottom throughout the entire grow bed up to the level of the standpipe before draining. And yes, they are fussy as Sylvia said. You also have to play around with the incoming water flow rate so that it is not coming in faster than the water is flowing out otherwise the water level will never get low enough in the grow bed for the siphon to break. Having a valve on the incoming water line will make life easier so you can help regulate the water flow.