Revolvers aren't "Old Guy Guns" (though, it's a funny moniker now that you mention it) but they do seem mostly obsolete.
Sure, revolvers can be fun, but my Beretta holds 15 rounds of 9mm, a Glock 17 holds 17 rounds, a Glock 22 holds 15 .40 caliber cartridges (or 17 with a special mag), the M&P series of pistols are high cap, Springfield XD, etc. etc.
Why would someone looking for a serious LE, SD or HD gun want a revolver? With between 5-8 cartridges, IMO it just doesn't make sense any more as a serious option for protection. Revolvers aren't fool proof, they can get out of time, things can go wrong, people shooting modern semi autos have reported thousands of rounds being fired successfully, with no cleaning , before a jam occurs.
To me, asking Revolvers or Semi Autos is like asking "horse or car?", "Light bulbs or candles" or "toilet paper or pine cones?"
It's just a no brainer.