The best (closest to the original) is the USFA (U.S. Firearms) Many think they are better than the new Colt SAA.
Rugers are awesome single actions. Beautiful guns. They dont have the 4 clicks, when cocking the hammer. And they have the transfer bar.
It just depends on how authentic you want.
In this pic. Left and right are American Western Arms. Their out of buisness now.
Center is an Uberti with old west finish.
Here's another pic of the Uberti. It is a fine gun, and I sure enjoy shooting it. For the cost, they are great!!!
Here is a pair of USFA SAA