If finances allow, the bigger styli collection you can develop the better the outcomes. When transcribing a 78rpm record to the digital domain, correct stylus selection can make the process significantly easier and more rewarding:

• Too wide - you will transcribe every surface defect on the record surface as well as needle distortions with the recording.
  This can make the de-clicking phase of the restoration process very time consuming or overload automated impulse noise filters resulting in signal loss or errors leading to unwanted distortion.
• Too fine - the stylus will drag along the bottom of the groove capturing more particulate noise from the groove base than the desired sound content of the groove wall. It can also result in a different type of signal distortion and a bad sound to noise ratio making noise reduction difficult.

The problem is that different makes and vintages of records have differing optimal styli requirements and the "one size fits all" approach really doesn't work. period! Many collectors swear by the Stanton 500 cartridge and styli that can be re-tipped with appropriate diamond sizes. These are getting harder to purchase pre-tipped but some information is still available at Esoteric Sound. They also sell a Grado range re-tipped with spherical diamonds. Shop around for the best deal.

Lists of styli sizes vs recording labels are somewhat misleading. The optimal stylus size depends on how many times a record has been played, the general condition of the record surface/groove wall as well as other factors like the pressing number and make. These all have a significant impact on stylus selection for optimal playback in addition to where and how a record was made. With that said, such lists can still serve as a helpful starting point, but you will soon develop your own optimal selection criteria based on your own circumstances and experiences. A review of styli sizes and their function can be found by Ron Geesin and Mark Berresford. More often than not you will end up having to try a couple of different sizes to determine the optimal stylus for playback. Don't be surprised if the optimal stylus size on one side of a record is different from the next. Similarly, two records of the same make/label and vintage can just as easily differ!

If on the other hand you are using something like the M78S cartridge then none of the above matters, just be aware of the impact stylus size has on sound reproduction during the transcription process and be aware this will have an impact on later noise reduction:

Bellow is a selection of records of varying vintage and condition played under the same conditions using a "Flat" preamplifier and no processing. I have also provided stereo vs mono for those who wish to compare the two. Note however, that as mp3 files (128 bit, 16kHz VBR) the stereo field may be somewhat narrowed. The reason it is better to record in stereo is that some records may exhibit more wear on one groove wall over the other producing more distortions and/or surface noise. If this is the case, it may be better to restore audio from one channel only!

The chart above is a plot of the lead-in groove surface noise level of the above ACO recording when played with differing elliptical styli: 2.0mil (yellow trace), 2.5mil (red), 2.8mil(orange), 3.0mil(green) and 3.5mil(blue) respectively. Note how that when played with a stylus of 2.5mil or greater diameter there was minimal impact on the de-clicked surface noise level between ~100Hz and 10kHz. Above this frequency range, the wider styli resulted in natural/mechanical roll-off of higher frequencies with styli of 3.5mil propagating more impulse noise and loud passage distortions into the recording. In this example, the optimal stylus size is somewhere between 2.5 and 3.5 mil.

Bellow is a selection of records of varying vintage and condition played under the same conditions using a "Flat" preamplifier and no processing with a 2.8 Truncated Elliptical stylus to compare to a 2.7-2.8 Spherical stylus. Theory says the truncated elliptical styli should out-perform the Shure M78S non-truncated spherical stylus which is more likely to drag along the groove/record base and pick up wall distortions. These recordings are chosen at random from my favourites - let your ears decide!

In the end go with your ears! Often I have found where a 2.5mil stylus works well, I get better results from the non-truncated elliptical/conical versions than I do the truncated.