If you want your magnum to be a "Magnum" the slow burners are the way to go. 2400 is the traditional magnum powder but many people think H110 and WW 296 give higher velocities. All three will give you a lot of muzzle flash and that nice magnum sound - you know, where the dust comes down from the ceiling at the indoor range and the leaves and grass are blown aside at the outdoor range.
I've been using 9.8 gr. of Blue Dot behind 158-gr. plated semi wadcutters, with a standard Winchester SP primer. It's a little less than full power, but it doesn't produce a lot of flash or bang and gives excellent accuracy in a 686.
I've been playing with HS6 in this caliber and unless you are into absolute max velocity with bullets over 158 grains, it gives a real good account of itself. Go to the Hodgdon's website and take a look.
When I was younger, an old-timer (probably my current age) had an excellent reloading book that recommended 2400. I like it because it uses quite more powder than others and makes it hard to throw a double charge. The barking dogs will reply that you should pay close attention to avoid such incidents, but things happen. It seems a bit messier than others, causing a more of a clean-up after the fun is over.
I am using the Hogden book max load of 22.0 gr H-110 with 125 gr JSP and magnum Win primers. Out of my S&W 686-4 6" I get about 1700 fps and quite manageable recoil. The report and flame are crowd pleasers. This load is also VERY accurate.
The only reloading I have done with the 357 has been using Red Dot for some light target loads. I hear very good things about Lil Gun though for hotter loads. I wanted to try it, and looked all over for it at the gun stores around me, but nobody stocked it. I even asked one place to order some in for me, but he never did, and has since gone out of business. I suppose I'll have to break down and order some online one of these days. But I really haven't had time for reloading lately anyway.