Given my profession, it will come as no surprise that my two choices are .38/357 caliber. Each I list I own, so I will add my reasons and circumstances of ownership.
The first is a Model 27-2 with the 3.5" bbl. It was my last duty revolver bought in the early '70s before my department switched to the Model 66, which became mandatory carry.
While I could have bought another Model 28 as I had previously owned, I simply wanted the nicest iteration despite no functional advantage. Despite its classic appearance, I ended up stocking it with Rogers grips because they fit my hand so well. As it turned out, it was only a short time until we went to the Model 66, so the 27-2 did not get carried much. It is in pristine condition.
My second choice is a 586 no dash with the 6" bbl.
From the time of its introduction I considered the L frames to be the ideal .38/357 duty sized revolver frame.
Our department had had a lot of problems with the Model 66s. About a year after the introduction of the L frames, Bill Davis made an offer to exchange our 66s for 4" 686s, and we would pay just the sales tax. I was able to make this happen for my patrol division (I was the division commander by then, and I was committed to getting my troops the very best equipment). With the departure of the 66s so departed the functional reliability problems. These 686s were our last duty revolvers until we went to semi-auto revolvers. They performed admirably.
As much as I like(d) the L frames I wanted one for me. I wanted a 6" 686 with the tall Patridge front sight for use in PPC leg gun matches so I could use a neck hold. But this configuration was thin on the ground. Finally a 6" 586 with that front sight became available, so I grabbed it. Since I wanted something that would replicate the stainless finish wear and rust resistance, I had the revolver electroless nickel plated. Next I had a gunsmith do a competition action job.
Next I had a brlliant idea, or so I thought. Wichita Arms at the time manufactured a stainless steel heavy weight barrel sleeve with an integral recoil compensator. I reasoned that this would convert the revolver to an ideal PPC competition gun for both regular PPC match use, then remove the sleeve via its hex head mounting screw for leg match use. Wichita recommended purchasers have them do the install since they were set up for it.
Upon its return I loved the considerably additional muzzle weight. On the range firing .38 wadcutters felt like firing .22 rimfires. This was one steady and slick revolver. Then I went to do some testing without the sleeve, in leg match configuration. There was however, one slight problem. That sleeve was not coming off. I figured that the very slight additional material on the barrel from the electroless nickel plating had resulted in the sleeve being so snugged to the barrel that no hand pressure would loosen it.
There went the bright idea of one revolver for both matches. I just continued using my PPC customized Ruger Six series for the regular matches and my 6" Python for the leg matches, since I was well satisfied with this combination. I still own both. Both too good to let go.
It was not too long after this that I quit competitive shooting. Command management responsibilities and college and academy teaching were taking up so much time that something had to go, and competition was it.
Given that I will not let a good gun go, I still have that 586. And with that wonderful weight forward balance and smooth action it is a great shooter.
Thus, my two selections along with far more information than anyone could ever want to know.
One poster had added the Colt SAA simply because it should be there. I second the motion.