Here's my perspective. I'm 47, about 6'1" and 220 lbs at the moment.
To me, the big divide in carry guns is between (1) a gun that is so light and small you can drop it into a jacket or pants pocket and forget about it, vs. (2) a gun that is big enough, and heavy enough, that you need a proper belt and holster.
In my experience, if you are going to "suit up" and wear a sturdy belt and good holster, there is little point in carrying a J-frame. Might as well carry a K-frame.
I actually find a 4" K-frame to be very, very comfortable. The extra barrel length makes it easier to carry because it stablizes the rig. If I don't want to carry something of that size/weight category, I usually drop down to a Seecamp .32, not a J-frame.
Everyone is different. You have to figure out what works for you. But what I discovered is that the guns that "obviously" loooked too big to carry were NOT, and the guns that "obviously" looked small and easy to carrey were NOT.