I have a variety of ponchos. The military one is nice because it is wider than most commercial ones and 2 can be snapped together for a nice "A" frame shelter. One makes a great bivi shelter.

I have a few commercial ones and the one I keep in my daypack is light and small, which is nice in a daypack. However, it is less useful as a lean-to because it is not very wide, compared to the military poncho. I recently went on a 3 hour hike and it started raining on the return leg. I had a Marmot PreCip Jacket on for a windbreaker and since it is a waterproof breathable, it was all I needed until the rain increased. I put the poncho on more to protect my pack than for myself. When I did that I noted that the width of the poncho was such that my arms were out below the elbow. If I had not had the rain jacket under the poncho, I would have had some wet, cold arms! So, pay attention to how big the poncho is, if you want to use it as a shelter or a rain jacket, it should cover the arms and be wide enough as a lean-to that it provides good coverage. Also, most "military-type" ponchos are just that, TYPE, they seldom are the size of the genuine military poncho, worth noting.