I have some thoughts...
I shoot revolvers in IPSC on a regular basis.
My preference for a game gun is an N-Frame Smith & Wesson. The gold standard for competition wheelguns is the S&W 625. This is a large frame (N-frame) six-shot revolver in .45 ACP. Using the .45 ACP cartridge makes for easy loading/unloading with moonclips. Moonclips, in my opinion, are the only way to go for a competition gun. The 625 is available in any number of configuarations: 4 or 5 inch barrels, short or full underlugs, etc.
The best buy on a 625 game gun right now is the 625 JM. JM is for Jerry Mickulek -- the "fastest revolver shooter in the world." For about $40 more than the standard 625, you get the smooth JM style wood grips, wider "speed" trigger, and gold bead partridge sight.
IHMO, the 625 JM is a great out of the box set-up. The only way to do beter out of the box is to buy the 625 Perfomance Center model -- which is quite a bit more money.
The only thing I do to my game guns is replace the mainspring with a reduced power version and polish/lube the internals. Oh -- and I usually remove the hammer block safety (that prevents firing if you slip while thumb cocking -- which I don't do).
If you must have a .357 magnum gun, the 627 Performance Center model would be a great way to go. Its a moonclip fed N-frame that holds 8 shots! Its also not cheap, and even the moonclips are a lot more expensive.
You could go with an L-frame gun like a 686, but very few come from the factory set up for moonclips, so you would have to have that done.
Again, my opinion, but the stubby fat .45 ACP rounds drop into the cylinder much easier and faster than the longer and more finicky .357 moonclips.
Anything else?
I have thoughts on holsters and moonclip holders too...
(How do you like the SP-101?)