Since you asked...
I think the 3" K-frames are the best-balanced carry revolvers. Not too big, not too small, not too long, not too short. It handles well. It carries well. The 3" barrel provides a full-length ejector rod. Out of the guns I've sold, my 3" 65 is the one I regret the most.
I don't really have an interest in L- or N-frames. The only L-frames that interest me are the.44s, the 3" 696 or the 2.75" 69. N-frames are too big for me.
The only J-frames that interest me are the 2" guns. The J-frames' biggest strength is their concealability. A 2" J-frame can be carried in a belt holster, shoulder holster, pocket holster, or ankle holster. A 3" J-frame can be problematic, at best, in some of those methods, and, to me, doesn't offer a significant advantage over either a 2" J-frame or a 3" K-frame.
I will add that I also like 2" K-frames. I used to have a 2" 64. Very handy size. Fast out of the holster. An added advantage of the 2" K-frame is that in the event of an attempted disarm, you'll have much more leverage over the gun than your attacker since you've got the full-size grip in your hand and your attacker has a little 2" barrel. For similar reasons, the 2" J-frame is considered one of the most difficult guns to disarm. For me, the 2" K-frame offers some of the concealability advantage of the 2" J-frame with some of the shootability of the 3" K-frame.
But nobody really has a "wrong" opinion. We like what we like, and prefer what we prefer, based on our needs/wants and intended usage.
TL;DR: 3" K-frames are ideally balanced for carrying and shooting, 2" J-frames are ideally suited for concealment.
Just my opinion.