The first thing to decide is "are you going to shoot it in CAS/SASS competition?"
If it's going to be a competition gun, you'll want fixed sights. If not, you CAN go with adjustable.
You also need to decide whether or not you want a transfer-bar safety and the ability to pack all six loaded, or no safety and carry "five up" (hammer on the empty cylinder).
The best choices in transfer bar guns is Ruger and Beretta. There's also the Taurus but the quality control reports are grim.
Among the Rugers, the mid-frame guns are the best quality control - that means the "New Vaquero" similar in size/heft to a Colt SAA, or it's adjustable-sight cousin the 50th Anniversary Blackhawk in 357. The larger-frame series are on average not quite as tight but good specimens can be identified via the "checkout" (see stickied post, this forum). They're larger and stronger, able to shoot the 44Mag or 45LC+P ammo that's as hot as the 44Mag and in some cases even wilder.
If you want a no-safety variant, Uberti dominates the low end and aren't bad...by "low end" I mean just a small step behind Ruger's quality. Some of the high-end no-safety guns by Colt, USFA, Turnbull and STI are just phenomenally good guns beyond anything Ruger offers, but also double the price.
Except for the USFA Rodeo.
The Rodeo is built as tight as other USFAs but has a much plainer finish. It's an excellent value.
Also worth owning are the Cimmarons, which are Ubertis, except that Cimmaron stations a quality control guy in Uberti's plant in Italy, does their own US-based warrantee and support program, etc. You'll get a better looking gun than the USFA Rodeo at around the same price, but mechanically the Rodeos are just awesome.
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My gun wasn't bought for competition - it's a shooter and CCW piece
. It's a Ruger New Vaquero in 357, modified sights, SuperBlackHawk hammer, spring kit, modified grips and...some "psychological warfare" action:
Absolutely no regrets, it's a sweet shooter. I am however considering an upgrade to either 44Spl or 45LC so I can get good power without going supersonic (major noise). With this class of gun, there's more raw power on tap in 357Mag than any other caliber...any of these modern Colt SAA clones can shoot the wildest Buffalo Bore, Doubletap or Grizzly Ammo "monster fodder" in 357, with up to 800ft/lbs energy on tap. As big-bores they top out around 500-550ft/lbs energy safely.