AEM and Snow make low budget PPS (progressive pump speed) systems, flow is based on boost pressure (single dimension).
Aquamist uses a high speed inline valve (as in OE cars), flow is based on flow flow. (3-dimension). If you want to know the difference between the system read this
link.
We manufacture 90% of our components in house and the others buys them from off-the-shelve plumbing or pneumatic supplies. Quality cannot be compared with aquamist. Aquamist is the only company that supplied all the works WRC teams (except citroen) for 12 year until WI was banned on 2006.
You don't have to be a rocket scientist to do an WI install, instruction is very complete (in general). Every kit install involves mounting a tank, a pump, nozzle in the inlet pipe and some electrical wiring. Aquamist is no more complicated than any other systems.