"Yosemite NP will be the most anal about canisters. They station rangers on the trail in Lyell Canyon specifically to check for proper permits and canisters."
Listen to these good words of advice above. Get a can - the BV is perhaps a few ounces heavier, but maybe $$ hundreds cheaper.
While most people consider a can either from the law (yes, Yosemite rangers treat the PCT like a highway stop on New Years eve looking for drunk drivers) and/or bears, I've come to see the advantages of using one even outside the parks from the perspective of personal convenience. The reasons for this are:
- I'm typically above treeline (which also implies no bears, but see below), so it's a drag searching for a suitable place to hang;
- I like to take my entire pack with me on all my side trips, like dropping gear and fishing for a while, and I don't want to d!ck around looking for a place to hang;
- Bears aren't the only critters out there - you leave your food unattended even for a moment, and either a bear can swoop down and grab, or most likely, while you're cooling your feet, taking a nap, and/or fishing, marmots and other rodents are busy eating through your pack/food containers.
- If you're doing major miles per day, the last thing you want to do is look around for a place to hang at the end of the day. It seems crazy, and maybe sacrilegious on this site, but for 2lbs, you get to roll into camp, pull out your sleeping bag, have something to eat, put your container somewhere, and crash. Ditto for the morning - get up, eat, pack & split.