Handgun holster retention levels; I II III, concealed rigs...
I strongly disagree with saying you need a level III type retention holster for CC use. A thumbreak or level II may be useful against loss, snatches, etc but unless you plan to work or be around convicts/prisoners a lot or work in a high threat area, weapon retention isn't as important as a swift, aimed response. A holster like the SFS or Blackhawk SERPA offers both speed and security.
A level III holster is best used for open carry, uniformed positions in high risk areas(courts, jails, LE offices, public/section 8 housing, airports, mental health centers, etc)