I saw the recent post about the MSR Guardian (Super expensive water filter). I currentley have the MSR MiniWorks although I need to buy a new ceramic filter replacement for the inside before my next trip to the High Sierra Trail to Mt Whitney in June. I recently stumbled upon the GRAYL ultra light and it has perked my interest, and I wanted to know your thoughts. I am deciding which one to bring on my trip, either get a new filter for my MSR or buy the GRAYL. It looks like the GRAYL has better filtering, it can filter Viruses, which I do not believe my MSR can? What are your thoughts on these two systems?