Hydration units are not worth all the fussing that they entail. Recycled plastic bottles make great, lightweight canteens - wide mouth Gatorade bottles are my favorite.<br><br>Packs are like knives - everyone's preference is different. This is a real distinction because our bodies are not alike. The most important aspect of any pack is how it fits you. In the store, load up the pack and walk around with it a bit to determine how it carries. It will feel a bit different at the end of the day if you have to carry it that long.<br><br>If 40 lbs is your absolute top limit, you need not look for a pack capacity of more than 4000 cu.in. There are lots of models in a wide range of prices available. You tend to ge t what you pay for. I don't personally regard the brands you are considering as particularly good, but I carry a pack a lot, in outdoors situations, and you are contemplating less frequent use, in emergencies only if I understand you right. Therefore, you might be able to get by with something less expensive and elaborate. Since you live in the Los Angeles area, you can't be too far from a branch of REI - they have a wide variety of packs that are at least decent quality or better - basically a good value for the money.