Is there a major difference between HAM and CB? For use in a disaster situation?
Yes, HAM radio uses 100's (when using VHF/UHF, or 2 meters) to millions (HF or 10 to 160 meters) of radio
frequencies - CB is limited to 40
channels. The types of equipment are similar (radios, antennas, feedlines), but the specifics are very different. For instance, high frequency (or HF) uses high power (100 watts and...above), whereas CB is legally limited in power to a maximum of 4 watts AM to 12 watts (PEP) on SSB.
CB, as well as the ham frequencies for VHF and UHF use vertically polarization - line of site - if the antenna is high enough those 4 to 12 watts will get you a few miles of range. The lower ham frequencies (from 10 meters/28 mHz to 80 meters/3.8 mHz) cover longer distances - to the other side of the world.
The big issue is this - since it is channelized - CB only offers 40 channels. During any emergency in a moderate sized town you will find 100's of people trying to use ANY method of communication
besides cell phones. I certainly wouldn't want to rely on 40 channels when the SHTF!
But - the increased distance, the more numerous frequencies - require a greater knowledge of power, electronics, and more specialized equipment (not to mention a keen understanding of safe operation). That is why the FCC requires testing and licensing, you really do need to know what you're doing.
Hope that helps!