After much confusion perusing many data sheets, I listed the major points by type in one place. However, there are those that claim it really doesn't make a lot of difference for audio quality. Not all values are available in all types, so you may need a mixture.
Here is the summary:
NICHICON ELECTROLYTIC CAPACITORS
TVX Axial General Purpose
USA General Purpose (USR smaller, UST high temperature)
USR General Purpose
UMA Standard, Low Profile (UMT high temperature, UMV long life, UMF low impedance)
UHE Miniature, Low Impedance, High Reliability (UHD lower life)
UKL Low Leakage
URS Low Profile (URZ high temperature)
URZ Low Profile, Wide Temperature
UPM Low Impedance, High Reliability (UPW smaller)
UCS Miniature, High Reliability, High Ripple (UCA larger, UCY smaller)
UVR Miniature (UKL lower leakage, UVK smaller, UVZ high temperature)
UVZ General Audio, Miniature, Wide Temperature (UKT higher audio quality, UVY smaller)
UKT General Audio, Wide Temperature (UKA higher audio quality)
UMW Standard Audio, Low Profile
UKA High Grade Audio, Wide Temperature
UFW Standard Audio (UFG higher grade, UKW higher audio quality)
UKW Standard Audio
UFG High Grade Audio MUSE (UKZ higher grade)
UKZ Premium Audio MUSE
UPJ SMPS Low Impedance (UPS smaller, UPV long life)
UPS SMPS Low Impedance, Miniature
UPV SMPS Low Impedance, Miniature, High Reliability
UPW SMPS Low Impedance, Miniature, High Reliability (UTT long life, UPA low impedance)
UTT SMPS Miniature, High Reliability
UDB Bipolar, Speaker Network
UES Bipolar MUSE
UVP Bipolar