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The most common mistake I see in people starting day hikes is not buying a bad backpack. It's buying the wrong backpack for what you actually need. They show up with a 40‑liter pack meant for two nights of bivouac, half‑filled, and after two hours of ascent you feel it: the dead weight of an oversized pack tires you more than carrying 2 kg of gear well distributed in a pack that, on the contrary, is suited to the hike.
How many liters do you really need for a day hike?
For a day hike, with food, water, an extra layer and a bit of first‑aid kit, the range that truly works is between 18 and 28 liters; anything over 28 liters is unnecessary weight in about 90 % of cases. Within this interval, the real decision isn’t “more or fewer liters” in abstract, but how long the outing will last. For a short outing, half a day, a couple of hours of ascent and descent, no extra margin is needed: less dead weight, you feel better on each stretch. For a full‑day hike, with more walking hours, that extra space and the comfort of the back system become indispensable and are noticed toward the end of the trek.
The two I use, depending on the length of the outing
Which of the two is right for you?
If your outing is short, half a day, a few hours on the trail, like a quick weekday escape, the Lithium 20 is the one I’d pick: it’s 300 grams lighter before you even put anything inside, and on a short outing that extra weight isn’t compensated by anything. If, on the other hand, the plan is a full‑day outing, with more hours ahead and margin to carry more food, clothing or contingencies, the Ducan 26 is the most sensible option, its back system comfort is felt especially after 4‑5 hours of trekking, just when a more basic pack starts to be noticeable on the shoulders.
Neither of the two is “the best backpack” in abstract, they are the best backpack for different types of outings. If you’re not sure which suits you, tell me what kind of routes you usually do and I’ll tell you which of the two I’d choose in your place.