Fuff,
I base my ballistic opinions on a number of things, not the least of which is several years of experience with people who'd been shot with various calibers, in various places.
Some of whom survived, and some of whom did not.
Bullet type, bullet size, and projectile energy does make a difference, and don't bother to mention "Placement is EVERYTHING", because it isn't, and with a gun you can't aim or hit with consistently beyond 10 feet you're even more handicapped in that regard.
You can't count on even a heart shot to immediately stop the other guy with a .38, you can't count on one shot in general to shut down a threat instantly, it's highly recommended that you be able to reliably strike an aggressive assailant attempting bodily harm on you with more than one round fired (which is where controllability comes in), and I've never bought into the .38 Wadcutter as being "good enough" to consider a defensive round.
It does not have to be a +P load, but depending on something like 2 grains of Bullseye behind a wadcutter's foolish, in my opinion. (And I don't use that 2 grains literally, just as an example.)
When I said I'd found I was able to use the old FBI one-handed crouch with good results, that was close up, using one specific grip style that made it impossible to aim, and I would not consider that one-hand shooting style to be effective at more than a few feet's distance.
The LCR has two primary selling points: light trigger and light weight. Those come with a pricetag attached; the price you pay is increased recoil with effective ammunition and a reduction in longer practical engagement distances.
If you think you'll only need to defend yourself at five feet, you're betting on statistics that may or may not turn against you.
If you think you can pull off a head shot under stress on a moving target with a gun you can't aim & can't quickly fire followup shots through, you may not be viewing this realistically.
Vod,
The Colt will have the lightest DA trigger among the choices you're mentioning, along with the ability to cock it for greater accuracy at distance, but be aware that Colt is losing the ability to service those, so if you go that route, get one as close to "new" condition as you can find, and also that the gun was rated by Colt for about 3000 rounds of +P .38s before it was recommended it be sent back for a checkup.
Today, Colt can't replace the frame if it stretches, and they're running out of hands (the most commonly-replaced part in a high-mileage gun with that older action).
Don't count on a local gunsmith for DS work, very few places left that can competently work on that action.
The Ruger SP will probably have the heaviest DA trigger, the Smith J-Frame trigger will still be much heavier than the LCR's trigger, both are capable of firing much more +P than the Colt, both are obviously still well supported by their makers.
Denis