None of the three systems you mentioned are independently tested and certified. Usually, it's a good idea to research before you buy.
First, don't automatically believe anything you hear, see or hear about. All companies say hat they are great and the other guys are bad...and this is rarely true. Check-out "www.lacsd.org" for independent reviews and "www.wqa.org" for independent laboratory results.
Moderated by Handyman 
