Independent tests have verified that EVC lights outperform both XM and Radium as well as other major brands of metal halide lamps on the market today by as much as 100% with respect to PAR readings. There value is unrivaled.
Be sure to check out the following articles with the bulbs tests:
http://www.advancedaquarist.com/issues/jan2005/feature.html
http://www.advancedaquarist.com/issues/feb2005/feature.html
http://www.tbaquatics.com/shop/search/results.html?search_in_description=1&keyword=evc