Cushioning and insulation are the 2 fundamental functions that a camp pad provide to us. They can provide a comfortable surface to us to sleep on and keep our body warm through providing necessary insulation to resist leaking of body heat to the ground. There are 3 major kinds of camp pads in the market, air pad, self inflating pad and closed cell foam pad.
Air pads are getting much lighter nowadays, and they are the most compact one being packed. This kind of camp pad should be inflated by your lung or a hand/electric pump, lightweight and comfortable, some of premium ones have added extra insulation for better thermal performance. These air pads should be paid extra attention to while using as they may get punctured or ripped( if you camp with your dog ). And this kind of camp pad tents to be more expensive than the other 2 kinds, the lighter they weighs, more compact they will be when packed. Some of the air camp pads may find leaking the air inside especially when the outside temperature diverse a lot. In those situations, you should only pump the air camp pad up just before you sleep.
Self inflating pads. This kind of camp pad is combined with open cell foam chambers and air to form its inflation system. Self inflating camp pads are convenient to be pumped up, you can just open the valve on its pad body, and its chambers will fill up automatically in very few minutes. You can adjust its compactness opening its valve for appropriate time to let certain volume of air being absorbed into this camp pad. If you need a relatively soft and thin one, you can just open its valve for a little while to let the pad absorb less air to make it a thinner and more soft one. Reversely, you can open the valve until the camp pad is fully filled with air to let this self inflating camp pad form a relatively compact one when you sleep or lie on it. Self inflating pad tends to be more insulated than air camp pads as they have the memorable foam layer within its chamber. But they are not as compact as the air camp pads as they can be filled with an air pump to the most compact limitation, the self inflating camp pads thought convenient using as they are, they have to be filled automatically and you can not inflate it with an air pump or your lung, that means they will stop absorbing air into itself to a certain extent. These self inflating one will not feel like leaking its air for a long time.
Closed cell foam camp pad. These are common foam camp pads filled with foam in many closed small cells. They are often folded into a long brick one for packing. They are lightweight, low price and easy care. You can just carry it outside your backpack without any package. This kind of pads is more tough as there is no problem of air leaking, punctured and cliff.
When you choose a camp pad for your camping trip, you should consider its requirement upon your camping conditions. For instance, if you are on a car/RV camping, size and weight is not restricted, you can have a larger and thicker one to provide additional sleep comfort. A 2 person self inflating pad will fit you well. As for backpacking camp trips, packed size and weight of your camp pad is significant. Bringing self inflating pads and air camp pads are appropriate to provide comfortable sleep and necessary insulation while lightweight and space saving. The spliced self inflating pads can be attached to each other compactly, very convenient for sharing tents with camp mates for backpacking trips. Referring to thru hiking, weight and tear resistance is crucial as you will pace a relatively long trail, closed cell foam camp pads is ideal for this kind of outdoor activity, they are lightweight, durable and easy care. And insulation is the most important factor for winter camping when you will usually camp on snow, keep an eye on the R value of the camp pads, the higher their R value the better thermal performance they will be. Usually camp pads with higher than 4 R value is suitable for snow camping. A high value air pad or self inflating pad paired with a closed cell foam pad is better. The closed cell foam camp pad will add extra insulation laid beneath the air pads/self inflating pads, and provide necessary thermal function in case the air pad or self inflating pads get punctured or leaking. For minimalist backpacking, ultralight weight and small packed size of the ultralight air pad is most appropriate choice.
Pay attention to the inflated size of the camp pads when you buy them, they should fit the ground area of your inner tent, usually an normal sized 2 person tent can be filled with 2 pieces of our spliced self inflating tents soundly.