Straight out of the box, OMs have a crisper and lighter trigger pull than NMs, however after a little bench time, all my NMs have trigger pulls that are just as good as OMs. It's not the transfer bar that causes a harsher trigger pull .... it's the way the factory sear notch is cut in the hammer.
ABNRGR, I paid $90 (tax included) for a NM Single-Six Convertible back in 1977. It is worth at least $500 today. Don't you think 5X is appreciation? A direct replacement (brand new Single-Six Convertible) has a MSRP of $799 so for the first few years, it will depreciate in value, then it will start to appreciate. In less than 5 years, a used NM will be worth more than it cost new. Guns are one of the very few mechanical devices that actually go up in value with age.
Some people just don't follow instructions and use procedures intended for other brands. This is true of all Ruger Old model Single-Sixes, Blackhawks, and Super Blackhawks where most owners use the old Colt SAA procedures with an empty chamber under the firing pin. If you look closely at an OM cylinder you will either see a firing pin groove or a non-recessed chamber and there is a very good reason, unique to Ruger OMs.
Here's a photo of some OM cylinders:
Note the top left cylinder. It is for a 45 Colt and the one below it is for a 45 ACP. Both have a firing pin groove. The next set of cylinders, just to the right of the 45 cal cylinders are for 357/38 Spec (top) and 9mm (bottom). These cylinders do not have a firing pin groove, however the case head is not recessed so it protrudes quite a bit. The next cylinders to the right are for 22 rimfire. The 22 LR cylinder (bottom) has a firing pin groove and the 22 Mag cylinder (top) does not. Seems there is always an exception and in this case, it's the 22 Mag cylinder that does not respond to the below technique. Last, the cylinder on the far right is for a 30 Carbine and it does have a firing pin groove.
So, what's the big deal with the firing pin groove or proud case head? It is Ruger's way of making it safe to carry all six chambers loaded. How? After loading all 6 chambers, pull the hammer back just far enough to clear the half cock notch then pull the trigger while easing the hammer fully forward. This will place the hammer in between chambers and because the fully forward hammer pushes the firing pin where it protrudes from the frame, the firing pin will lock the cylinder between case heads and prevent it from rotating. If the cylinder has a firing pin groove, the distance of the firing pin travel will keep the firing pin from touching the cylinder to prevent firing pin damage. OM cylinders without a firing pin groove will also lock the cylinder between case heads and because the firing pin has a forward limit in the frame, it will not touch the cylinder face. So, you end up with all six chambers loaded, the hammer fully forward, the cylinder locked between case heads. This is just as safe as using the Colt method, plus it allows all chambers to be loaded. If you want to test your OM, load it with 6 empty cases because it won't work without cases in the cylinder.
As for bluing .... many Old Models had very poor bluing jobs at the factory, and in time, the frames and loading gate turned a plum color. Collectors like defective products so "plum guns" tend to be worth more than those that were blued properly. Some of the early Old Models had a polished finish that looks very nice, but this only applied to a few years of production. OMs made after 1966 have the same blued finish as current New Models.
Clicks .... some people are infatuated with the clicks made when cocking the hammer. NMs have clicks too, only they are a couple short of an OM. The first OM click comes from the hammer safety notch. The second is from the hammer plunger releasing the cylinder latch. The third click is when the hammer passes the half cock notch, and finally, the fourth click is when the hammer locks into the full cock sear notch. NMs don't have a safety notch nor a half cock notch so you only get two clicks .... one from the hammer plunger and one from the full cock notch.
Safety .... NM Ruger SAs are the safest single-action revolver ever made by any company. Not only do they have a transfer bar to prevent at least three safety issues, they also are loaded with the hammer fully forward. This prevents "thumb slip" that can happen with an OM after loading, Further, the action is interlocked so the hammer cannot be cocked when the loading gate is open, and the loading gate cannot be opened when the hammer is cocked. Besides collector value, the NM design is my prime reason not to fire my Old Model SAs.
THIS is the best explanation I've ever heard !- compiled with experience, knowledge! Thank you! Ruger should have this on their website! And, because of this, it just confirms that the Ruger Single Action revolver is the best production revolver ever made! Now, if I could just get Ruger to make the 357/360 Bisley with an unfluted cylinder (for those heavier hunting loads - shooting cast boolits)!