I have shot both revolvers and autos extensively for 45 years or more. I have seen plenty of malfunctions with both platforms. In general, I probably trust a revolver slightly more, after it has been proven to be a good reliable revolver. I have found that most revolver malfunctions show up as factory defects and once proven reliable are usually very reliable, for a long time until they get dirty, or suffer parts wear or breakage. The rest of the malfunctions are ammo related, usually. High primers, and powder granules under the extractor are the most common issues, but of course a squid load can tie one up, and shut it down.
Semi-Autos once again, after a particular semi-auto has been shot and proven reliable, they usually remain reliable, until parts wear, parts breakage, bad ammo, or becoming excessively dirty, however there are a lot of other things that can go wrong and one needs to vet the particular semi-auto extensively to learn if there are any issues including operator issues. And sometimes those operator issues take a little time to crop up. Poor magazines are one of the most common issues with semi-autos, and also factory defects. And some people have problems with weak wrist or weak hold, and not giving enough resistance for the slide to work. This is a problem my daughter has with several models of Glocks, but the very same pistols in my hands hands have proven to be 100% reliable. But her Smith and Wesson M&P Compact 9mm works 100% for her.
My favorite semi-auto and also the carry gun platform I carry CCW the most often is a 1911, usually a Colt Lightweight Commander. However, I have had good reliable 1911's with 100% track records, suddenly become very unreliable, and its usually always been a broken or otherwise failed extractor. But once replace and tuned correctly, went back to being 100% reliable.
And I experienced a stoppage with a Wilson Combat 5" 1911, one time, caused by a squid load which deserves mention. I was shooting a fast stage in IDPA competition. I was shoot some custom reloaded cast lead reloads, 200gr lead semi-wadcutters. the last round in the mag did not have any powder in it. The primer shoved it into the barrel, but I was wearing muffs, and did not hear the faint sound of the primer and just thought that my slide did not catch open on the last round, so I racked the slide back to lock, dropped the spent mag and reloaded with a fresh mag and dropped the slide and finished the stage. All round were on the target with none missing. I was a little mystified, because I did not understand exactly what happened, and shrugged it off. But in practice at home, I had the same thing happen the next week, but I did hear the primer pop, this time. So, I pulled the slide back and sure enough a bullet was in the barrel just ahead of the chamber. I decided I would not buy that gunshow custom loaded ammo anymore and regulated the rest of that ammo to practice only.
No damage was done to the gun, that I could ever detect. It might have been different with jacked hardball, I don't know, but the softer cast lead bullet was harmlessly pushed out the barrel and actually landed on the target, in the IDPA competition stage. Now, I have had squid loads (no powder) before, when using a revolver and every time it ever happened the the bullet locked up the cylinder, and the had to be driven back into the chamber before swinging out the cylinder. In this case the semi-auto handled the malfunction better, and hardly slowed me down at all, in competition.
I trust my handloads, but I don't trust other people's reloads, even custom reloaded ammo. In a self defense gun, probably only top quality factory ammo should be used, and that will reduce the odds of a malfunction, regardless of revolver or semi-auto. I trust small revolvers better then I do small autos, but larger full sized autos, if top quality, are probably about as reliable as revolvers and easier to carry for me.