I think that part of your decision should include your plans on black powder.
I am very happy with my 357's with a 4.75" barrel for light smokeless "cowboy" loads.
If I load 'em up with blackpowder cartridges, I wish I had the long 7+ of the original SAA.
You have to load black powder cartridge to full capacity, it is not safe to do otherwise, so the short barrel does exhibit noticeable muzzle flip when compared to the heavier long barrel.
My heavy 8" Navy cap n ball has much faster target reaquire than my SAA, but again, only with blackpowder.
My revolvers are 357, but have seen a lot of 38 through them. I found 357 shells cycled through my rifle more reliably, so now I only shoot 38 for practice. I have found a nice load of Trailboss under 158 grain hard cast lead that is safe and consistent in both cases (3.2 gr) so only one setting on my powder measure. It makes 357 the same price to shoot as 38, right in line with required velocity for SASS, and very comfortable. Starline 357 brass is not much more expensive than new Starline 38 brass either.
A beginners kit from Lee and a set of dies will pay for itself half way through your first season. You can find a load your guns like, and be assured you can always get it.