Everyone knows that not all lenses are created equal. It's therefore logical to conclude that not all filters are created equal either. Given that there is a big disparity between glass quality from manufacturer to manufacturer, are you aware that there is a difference in how water resistant they are? If you are wondering isn't all glass waterproof? The answer is yes, but some glass more than others.
Why does this matter and how much more waterproof can glass get? It matters because it determines how easily it can be cleaned when it gets dirty. Today many manufacturers have incorporated a nanotechnology also known as hydrophobic. This technology is responsible for making many products waterproof like the Samsung Galaxy phones. So how does the technology work? This technology works by making water bead at a much steeper angle than usual and therefore water slips off the surface rather than spreading. With this very steep angle, the technology is essentially creating viscosity. So when grease from your fingers gets on your filter it is much easier to clean, because the grease has not been allowed to spread out on the microscopic level.
We all know that we will eventually get our filters dirty. Having a filter with nanotechnology will make it much easier to clean.