While I do not carry a .22 caliber firearm for protection, it does have several advantages. As seen at WND.com, Molotov explains why a .22 caliber weapon is an excellent firearm, including for those carrying concealed for personal protection. After watching the video, check out the link here for actual data statistics on different calibers of bullets and be fully informed on the comparison.
UPDATE: Many have "poo pooed" the use of a .22. These guys demonstrate the .22 can produce a lethal wound.