For the sake of revolvers, let's point out some obvious apples the oranges comparisons that revolver haters like to use.
Reloading: A lot of semi fans like to compare reloading one round at a time into a cylinder to the speed of putting a loaded mag into a semi. A reasonable comparison would be reloading with a speed loader or moon clip versus changing cylinders.
Steps for a semi: Eject spent mag. if it's a free drop mag then this goes faster, otherwise there's the time to pluck out the previous mag. Then insert next pre loaded magazine. Rack the slide.
Steps for Revolver: Open cylinder and eject spent casings. Probably the slowest part of the process versus ejecting. Load fresh rounds via speed loader or moonclip, close cylinder.
Roughly the same number of steps. Ss a revolver reload as fast now? No, but the difference isn't nearly as drastic as the detractors make it out to be. Now if you want to talk about reloading without speed loaders, the revolver still chambers 5-8 rounds. How well does a semi work without a magazine in it?
Next up, power. We can argue 9mm vs .38spl all day long. 9mm is faster, 38 is heavier, pick your your lead posioning.
But in higher calibers revolvers have the clear and obvious advantage. .357 sig can sort of scrape the bottom of .357mag on the low end but not on the high end. Yes you can get similar velocities to .357 mag by cutting the bullet weight, but you're not going to get the high end performance from sig that you get out of hot loaded 158, 180, and 200gr load. The .357mag with its heavier round and greater space for powder has far more potential than sig can get. By the same argument while the 10mm is a potent round, .41 mag again has the greater high end performance. Same goes for .45acp and .45lc and that's before we even get into .44 mag, .454 Casull and .500S&WMag, but at that point you're getting into hunting and large predator defense. Sticking to practical rounds for personal defense, .357mag still outshines .357 sig as long as the shooter can handle the recoil.
It's capacity versus power. Arguments can be made for both, but you can't argue that semis have both. A frame that's designed with more moving parts, and to utilize X amount of recoil with Y spring to absorb said recoil has an upper limit to how much it can handle. That's a limitation of a mechanical device. A cylinder can only hold so many rounds without being too large to be practical, a slide can only handle so much recoil. It's always going to be a trade off. Personally I carry a revolver in .357 magnum. It's no secret that I just plain prefer revolvers, but I'm also a pragmatist with self defense. I chose to carry this particular gun because I have my doubt in the ability of non-magnum rounds to stop a threat. I've heard enough horror stories of 9mms failing to stop, and .380's bouncing off skulls. The .357 is a round designed from its inception to penetrate even through heavy car doors of its era. I don't doubt its capacity to take down a threat, and I'm willing to give up some capacity for that stopping power. A semi fan might not trust their own accuracy or believe themselves more likely to encounter threats in large groups, or simply believe it's preferable to make multiple weaker hits than a few more effective ones. I suppose there is credit to the saying I once heard "regardless of scale, things tend to die if you put enough holes in them."
The last argument I want to make is reliability. The OP made the biggest apples to oranges comparison putting a sig against a taurus. Now that's just silly. Mind if I compare my Dan Wesson to a Hi-Point while we're at it? Fact of the matter is, a revolver cocks and loads via the power of the shooter its self. A semi relies on a round having the right amount of recoil to compress a spring, and springs to have the right amount of strength to perform their duties. When I pull the trigger on my revolver I know a bullet is coming out of it. I just can't trust my life to a device that has so much of its duties out of my hands. In a confrontation, you may not have the time to clear a malfunction. Then there's the issues of various safeties which have been covered before.
Capacity is an argument that goes in favor of double stack magazines, but the ever popular single stack 1911s and mouse guns, the capacity argument is pretty well mitigated. Double stack guns of course sacrifice some of their concealability, but the point here isn't to entirely say that semis don't have a capacity advantage, but to point out that not all semis, particularly some of the most popular right now.
All in all revolvers are a valid choice for power, simplicity of operation, and reliability versus capacity and SOME reload speed. For military and police purposes, when you have someone else to cover you while you clear a malfunction, that's fine. When it's one on one, I'll take the revolver first every time. I won't totally detract from semis though. When it comes to getting them truly tiny, the recent wave of mouse guns have gotten impressively small, and flatter than any revolver ever could. So in a case where you just can't carry a higher powered gun, and a mouse gun means the difference between SOME gun and NO gun, then a semi shines in this area. I myself plan to get one for backup and cases where I might have to dress in a way that doesn't allow carrying my revolver. To say that revolvers serve no practical purpose is rediculous. If anything they're more valid than ever as need arises for powerful, reliable, and easy to use weapons as more and more Americans choose to practice their 2nd amendment rights.