The revolver can be fired in many situations when a semi auto would be reduced to being a single shot(eg. from a pocket or from under the pillow) . Revolvers with a shrouded or internal hammer, since they do not rely on ejection of the fired case and feeding of a new cartridge, will fire when enclosed and even up side down. I tend to pocket carry most of the time. Possibly if I weren't just too cheap to buy a good IWB holster it would change my choices. Revolvers have a "lumpy" profile which tends to conceal that profile in the pocket. A semi auto profile is flat and tends to look just like a gun when carried in your pocket. A pocket holster will help some with the profile but will do nothing about making a automatic pistol fire in all situations / positions. These reasons are the ones that compelled me to carry a revolver. My poor little PPKs just pines away in the safe, looking racy. What I tend to carry most is a 638 Smith&Wesson loaded with 125grain hollowpoints. It is light, accurate, and even kind of cute, in a deadly way.
Wakatomika