>>2547076That looks like a cancer bag desu but a side zipper is extremely useful when you carry a lot of different stuff, or simply 2 to 3 weeks worth of food.
I think Exo has the best bag design. Easy to get to your food bag without having to pull out your tent, or get to spare socks, heavy baselayer without having to pull a 30 pound food bag. You'll appreciate side zippers when you have to carry winter gear / extra gear, in autumn weather, or simply when it's several weeks between resupplies.