Tants are often specified as the DC reservoir caps in the voltage multiplier circuits due to the HF nature of the charge/discharge cycle... I cannot for the life of me conceive of how one can ever "sound" better than another in this application: either they store enough charge or they don't. There are usually a couple of stages of R/C filtering, so you get smooth DC out at the end of the line. DC always sounds the same...
If that's the application and you're asking the question, you probably don't know enough to work out that there is no effective difference...tantalum is tantalum, it works well in the HF area, and good enough is the same as perfect. -In this case I quote Mary Poppins:
"enough is as good as a feast"
Just put whatever tantalum caps you can source in, and stop worrying.
Keith