I wanted to follow this up with some additional thoughts that might provide some insight. You asked a very general question, and provided almost no criteria or background as to why one might consider those different frame sizes. I’ll share a little history that influenced choices between them.
Back when Police Departments issued revolvers, Officers could be issued a different model depending on the job he did. Officers serving on large police forces or big metropolitan departments often saw changes in gear when they moved from uniformed patrol into a plain-clothes post or an office job. Many small departments wouldn’t spend the additional money on different models and the leather, but sometimes individual officers could, and if they could they often did.
If the department had contracts with Smith and Wesson, patrol officers were usually issued one of the models of the K or L frame revolvers. If it contracted with Colt, about the smallest size frame Patrol got were the Official Police. Colt Troopers and Lawmans were also common.
Without a wide duty belt those big, heavy large frame revolvers get uncomfortable. If the department didn’t have anything smaller to give him, when an Officer got to the office in the morning it was quite common for him to take his gun off, lock it in his desk drawer for the shift, go about his day, and only take it back out when his had reason to leave the office again. And not to discount the work they did, but those working in detective billets, department supervisors, and Chiefs of Police just didn’t go do jobs that required all the gear patrol officers carried. They didn’t take calls for service, and they wanted less. And men in positions like Chief of Police tend to get what they want. Both Colt and Smith responded to that market. The 2 inch Smith J-frame and Colt D-frame (Detective Specials, Agents, and Cobras) gained in reputation as commonly issued gear to plain-clothes officers like detectives, supervisors or others spending most of their time in office environments, i.e. - officers not going out on patrol.
Patrol Officers carried a working gun. The brass carried those small guns. They were harder to qualify with; harder to shoot well; harder to reload; they were harder to do pretty much anything with if you actually needed to use one. But they had one important characteristic that only really mattered - they were more comfortable to carry around all day long wearing a suit. Over time the Colt’s Detective and Smith’s Chief Special became regarded as something of a badge of honor, if you will, reserved for those senior officers.
As the carrying of concealed handguns by armed citizens became more acceptable by society, the buying public was attracted to those small guns for the same reasons. And by the end of the 20th century concealed carry became more than just socially acceptable, some states required it. Openly carrying a handgun became objectionable, or even unlawful in some places, much in the same way concealing one in the 1800s was. J-frames and Colt D-frames conceal much easier than that Smith K-frame will. They’re more comfortable, and they don’t need the support of a sturdy belt. With the advent of aluminum, titanium and now scandium metals, many people stick one in a pocket and don’t even use a belt at all. But they are harder to shoot.
And that’s the challenge between having something that conceals well, and something that you can make work and shoot well. If I thought I might actually have to use it, I’d carry something bigger than a J-frame. A lot of Officers carried one around because the job said “yes, even if you’re in an office, you’re still an Officer and you have to carry a gun”.
