Revolvers have an edge in reliability and ease of operation under the stress of a gunfight. No safeties to worry about, just pull the trigger. No magazine to give issues, dirt is less of an issue, ect.
However, depending on the semi auto, you will have an edge in trigger pull(Single action), ammo capacity for size(usually.)
Now, I have owned a Ruger police service six snubbie in 357 mag, and I ditched it for a semi auto years ago. If you take care of your semi auto, and its a quality gun, I see very little reason to pick a revolver most times.