I've used a few of these in the past - from some no-name unit in the late 80s and 90s that required the filter to be submerged up to most recently a MSR Hyperflow. None of them are much fun to use, some are faster than others. They all work and all cost a lot of money, and all weight a pound or so. For a short Whitney tour, any will do. Or just drink smart and bring some Aquamira pills or bleach if in doubt.
I've read about water on Whitney and there are several places that are safe to use without filtration. Always go to inlets of lakes or the waterfall at Bighorn Park. On the other hand, the Whitney Zone is one of the highest use areas of the Sierra, so it isn't necessarily the place to take chances.
a water source map for the east side of Whitney:
Been looking at the Steripen for winter use when normal filters are a bust, but I'll probably be melting snow most of the time anyway, or just take my chances. Giardia and many other bugs don't survive freezing temps anyway and are re-introduced each season.
