I have mats of both types. They are both adequately comfortable. Both are about 1/2 " thick. The foam mat is a little more comfortable than the selfinflating one. The foam mat is more robust and makes less noise but it´s considerably bulkier. The foam mat can also be stored in a packed state which makes it possible to leave it in a vehicle. I usually use my foam mat when bulk is no issue. If bulk is not important I´d go for the foam mat.
I also have a 5 mm aluminium covered foam mat. This one is not very comfortable but it keeps the moisture away. I keep it on my motorcycle as first aid supply.