Reproduction versus original parts is a debate that comes up sometimes among old bike enthusiasts. There is an overwhelming preference for original parts. However, sometimes a reproduction part needs to be used. Sometimes the rider wants the smoothest possible drive train, or the straightest and truest wheels. This can mean that old parts are dropped in favor of reproductions.
So is something lost when we use a reproduction part? Sometimes yes, and sometimes no.
Tonight, let's look at the reproduction "classic cruiser" Schwinn-type sprocket, versus an original Schwinn 1950s-60s era sprocket.
The original is on the right (mounted on the bike) below. The reproduction is in my hand on the left.
As you can see, the shaping of the original is crisper. The plating is also deeper and cleaner. The metal on the original is heavier gauge and seemed a bit harder. The original does have a little wear on the teeth, but plenty of miles left. I'm going with the original, though I will admit I had to true the sprocket using a big crescent wrench.
So why would you use the reproduction? The reproduction is a little straighter. If you didn't want to true the original, then you could drop the reproduction in, and the drive train would run reasonably smoothly.
I think the answer to reproduction versus original is to run original parts whenever reasonably possible for a working bike. However, if the choice is between a broken down bike with original parts or a working bike with reproduction parts, go with the repro and put the bike back on the road.