Wait. Let's start with the basics.
What do want it for? Woods carry? Street/CCW? (And yeah, some do
.) Cowboy action shooting sports? General shooting/target?
What's your budget?
Do you want something that has a modern transfer bar safety inside even if it otherwise looks "old school"? There's a few such, and can be safely carried six-up. Anything else, it's five-up, hammer down on the empty just like Wyatt and anybody else back then did it if they were halfway sane (not all were of course...).
What caliber? 357/38 is cheapest to shoot if you're on a budget. 45LC is both traditional and fairly easy for a beginner reloader to cope with. The vintage slightly bottleneck cartridges like the 38-40, 44-40 and 32-20 can be kinda nice but are more difficult to load.
Do you want traditional sights, or adjustable like the Colt "New Frontier"?
What kind of budget are you dealing with?
How much do you care about looks?
That's a start on just the questions
.
For the record: I have a matched pair of near-clones of the Colt SAA. Primary, and daily carry CCW is a heavily modified Ruger New Vaquero in 357, 4.68" barrel (what Colt would have called a 4.75"), blue, transfer bar ignition. I have a piece that's purely for cheap practice as an "understudy", a Cimarron "Plinkerton" $200 .22LR modified to mostly match the Ruger. The Plinkerton is not at all "heirloom quality" and I wouldn't trust my life to it, but it works well as a cheap practice gun and alternative to high-volume reloading...you can shoot .22LR cheaper than you can reload 38.
Ruger makes a good gun, and the NewVaq is fairly close in size/heft to a post-WW2 Colt SAA. The ergonomics can be retrofitted to match a pre-war Colt SAA fairly easily as I've done by dropping in a SuperBlackhawk lower hammer. Doesn't look very "cowboy" but it matches the pre-war thumb reach to the hammer.
USFA copied the pre-war Colt ergonomics out of the gate on most models including the Rodeo. Higher-end-finish model USFAs run around $900ish and usually exceed Colt quality control levels at least a little; a few years ago they were beating the snot out of Colt and Colt reformed their production standards in response, almost catching USFA. Almost
. Colt, USFA and most of the Italian guns are all either "no safety at all" or in the case of some Italians, "safety that can't be trusted six-up" - either way, they're for five-up-carry.
What else...ah. Take a good look at Longhunter, a gun dealer and gunsmith who has good deals on "pre-tuned" pieces:
http://www.longhunt.com/
He weeds out any "birth defect cases" from the Rugers and high-end Italian pieces he sells, and on USFAs he replaces a lot of the internal flat springs with modern coil springs. He's highly regarded.
Finally, if you have the money, the very best single actions made today don't look very traditional, but they have the highest machining standards of anything this side of the engine in a stealth fighter. That's Freedom Arms. Nothing, and I mean *nothing* beats their quality control levels or out of the box accuracy. They make Colt or anything else outside of maybe a 1960's-era Python look like a joke. My ultimate dream gun is a Freedom Arms '97 model, 357Mag, six shots, 4.5" barrel, round butt, adjustable sights, octagonal barrel, extra cylinder in 38 match chambers. List, about $2k. Worth it? Check out this test of that gun in 22LR that managed an honest 1" group at 100 yards:
http://www.gunblast.com/Freedom_97-22.htm