A daypack is pretty useful on a Philmont trek, but only if it is really light. The Gossamer Gear Riksak is 2.9 ounces and doubles as a stuff sack. It is made of silnylon and costs $30.
At $35 and 4.6 ounces, the Gossamer Gear Riksak 2 is made of tougher material and has proper shoulder straps instead of slippery silnylon sleeves. That could be a worthwhile tradeoff if your side hike is more than a mile or so.
Why a daypack on a backpacking trip? Every Philmont crew does a three hour conservation project. You could empty out your pack, but all you need for “cons” is rain gear, a first aid kit, and water, so a daypack is perfect. Side trips for peak bagging are pretty common on Philmont itineraries, so a daypack is great for those, after you bear bag the smellables, of course.
Once you have a daypack with you, it is just the thing for a the ten essentials and a camera for all the Philmont activities. It is also handy for heading across base camp, or even on the trip to Philmont.
If I was choosing the best daypack for a hike, it wouldn’t be the original Riksak and might not be the Riksak 2. But as an extra item to carry on an twelve day 50+ mile trek, they are just right.