The sound that you hear vs. the sound on the recording
Belfer Audio Archive, which is one of the largest sound archives in the United States, and a quick walk from where I work. Besides looking that their collections and listening to recordings on cylinders, we had a chance to talk with Robert Hodge, who is the audio engineer and the person who is transferring sound from these older formats to digital files.
From Bob's talk, I left with two interesting examples. First, Bob demonstrated how the sound quality of audio recorded at 78 rpm changes depending on the stylus used. I grew up with a record player that would play 45s, 78s, and 33s. We used the same stylus (needle) for all of them. The sound, though, is better if you use the correct stylus on the 78s. Obviously, I think, you should digitize using the correct stylus and equipment for the recording. In the metadata, information on the equipment used should note that decision.
Second, when you play an old cylinder recording, as an example, using the technology of that era, you are hearing what that technology allows you to hear. However, what if you can play the recording on better technology and hear more? While that will be pleasing to your ear, which version is correct? Which should you digitize? One organization might decide that using the original equipment is correct, while another might want to retrieve the actual audio that is on recording, and both would have made the right decision. What matters is that the metadata convey how the digital version was created, so that a decision such as this is known.