Maria Diaz/ZDNET Follow ZDNET:  Add us as a preferred source  on Google. At ZDNET, we're all about putting tech to the test to actually see which phone has the best battery life or which robot vacuum has the best pickup performance. And when we tested 10 different robot vacuums in our lab, one was the clear winner. Also:  We compared 10 robot vacuums for sand pickup - and one model was the clear favorite The Ecovacs X8 Pro Omni had the best average score for sand pickup on both hardwood flooring and carpet. And right now, it's $51 off at Walmart, meaning you can snag this Lab Award-favorite for $599.  Compared to the other robot vacuums we tested from brands like Shark, Roborock, Dreame, and others, the Ecovacs Deboot X8 Pro Omni picked up an average of 60.28% of sand across all three of the testing categories (hardwood floor, low-pile carpet, and mid-pile carpet).  Aside from its impressive pickup performance, the Ecovacs Deboot X8 Pro Omni has a self-cleaning mop roller and has a…