How does the string tension of the D'Addario EJ26 Custom Light set compare to the EJ15 Extra Light set, and would the EJ26 be suitable for fingerstyle playing on a vintage acoustic guitar with a delicate top?

The D'Addario EJ26 Custom Light set has slightly higher string tension compared to the EJ15 Extra Light set, which means the EJ26 will feel just a bit firmer under the fingers. While EJ26s can work for fingerstyle, if your vintage acoustic has a very delicate top or you want the lightest tension possible to minimize stress on the instrument, the EJ15 Extra Light set may be a safer choice. The EJ26s, however, offer a good balance of ease of play and fuller tone if your guitar can handle a little more tension.

Is there any noticeable difference in tone or longevity between the D'Addario EJ26 Phosphor Bronze Custom Light strings and the EJ16 set, especially when used on a smaller-bodied acoustic guitar?

The main difference between the D'Addario EJ26 and EJ16 strings is their gauge. The EJ26 Custom Light set is lighter (11-52), making it easier to play and often producing a slightly brighter, less full tone, which can suit smaller-bodied guitars well. The EJ16 set is Light gauge (12-53), offering a bit more volume, warmth, and sustain, which can enhance projection and fullness. Both sets have similar longevity and are made from the same phosphor bronze material, so durability is comparable. If you prefer easier playability and a brighter sound, go with EJ26; for a fuller tone and more projection, choose EJ16.