Kellar is very kind but I'm just an ordinary member here like everybody. I'll try to give you a few opinions. I agree with what Jim just posted, and Stephen's articles are the best.
Most opinions that you can find will give the edge to the .38snub over a .380. Both are fine as civilian, last resort self defense handguns but many that travel in risky areas will only carry them as backup. You have to practice with any caliber to have confidence. A .45 is no good if you can't hit the side of a barn with it. "Placement", accuracy, is what counts, not the best ammo in the world if you can't hit the target or it hangs up in your gun.
About the only ammo I've found with a "truncated cone" for the 380 is cheap Win WhiteBox Value Pak, 95gr, at WalMart, and it's considered just an ordinary FMJ round, no better penetration than standard round nose FMJ. And it won't mushroom like standard hollow point ammo.
I wouldn't carry FMJ in a 380 due to possible overpenetration and hurt an innocent bystander. OK for target practice, but I don't carry it for self defense.
If you choose the 38snub, it's best to stick with something like Speer 135gr+P JHP or one of the rounds you read about in Stephen's articles.
For the 380, your Walther I assume you have, there are a number of excellent JHP rounds on the market now. You have to try whatever you can get and like the looks of, shoot a box, to be sure it will function without any FTF or FTE. Then stick with that ammo for carry. Good choices that we have tested to choose from include Remington GoldenSabr 102gr, Hornady XTP 90gr, Winchester SXT 95gr, and the new CorBon DPX 80gr copper bullet JHP. Some like the Speer GoldDot 90gr too. I leave the final choice up to you after you fire it in your pistol to prove it functions 100%. Try several brands if you can.
I tested the above rounds in a Sig P232, very close to the same barrel length as the Walther. You can check out the results here....for most brands....
and here....for the CorBon DPX....
For 38special tests, Stephen's articles are still the best.
Oh, BTW, one advantage of the 38 revolver is most ammo functions fine without problems that a semi-auto might have.
My wife's home handgun is a S&W model 37-3 with CrimsonTrace laser grips, loaded with 38special Rem GS 125+p and Speer 135+p JHPs.
(Edited to correct 38 special loadings.)