Aquavideo are a US company that have been around a long time and have an impressive list of customers including NASA and Stan Waterman. Their philosophy has been honed over time and is focused on what works best rather than what looks good in a catalogue. AquaVideo housings are PVC construction with some rather neat welding techniques employed.
Seals are x ring for reliablity.
Certainly their systems benefit from the mechanical control approach. Another advantage is that an Aquavideo housing can be easily adapted to new models when you upgrade your camcorder.