Hello Steve, Why not try out both of them as a live disk (one at a time of course) with No installation nessesary! Just download the two versions and tell your disk “burning” software that you are making a disk from an “iso file”. Depending on the disk creating software you use, you might also try telling it that you are duplicating or copying a disk, and, when it asks for the original, point it at the “iso file”
Most computers can boot from such a DVD by simply placing it in the tray and restarting the machine. If yours does not, you might have to make an adjustment in your B.I.O.S. setup utility.
As for differences between the two: “Carbon” might be slightly better for very old computers because it is based on an earlier Linux “distro”. “Air” will have more updates and more software and is based on a newer Linux “distro”. Overall, Most users will want the newest.